Hi Fiona,
I'm sorry to hear that Archie has chronic pancreatitis. My Saoirse has it as well. I hope some of the following might be of help.
First up, the IDEXX pancreatitis treatment guide has recently been moved to a different location on their website so the link in the FDMB Pancreatitis Primer doesn't work any more. Here's the up-to-date link to this very, very helpful document:
IDEXX Treatment Recommendations for Feline Pancreatitis
Although Tanya's Site's main focus is CKD, there is a great deal of helpful information about identification and treatment of
nausea and inappetence problems, a lot of which is relevant for cats with chronic pancreatitis. There are many natural and medical treatments described there. On the site you will also find good tips on how to encourage a queasy kitty to eat.
Some of the meds used to treat/manage pancreatitis can be constipating (bupe, ondansetron). A helpful site in this respect is
www.felineconstipation.org. I've started adding canned plain pumpkin to Saoirse's food along with extra water to help keep her properly hydrated (she stopped drinking from her bowl after I switched her to wet food and her BG became better regulated). From what I've observed of Saoirse, constipation can make a cat with chronic pancreatitis feel a lot worse. (The pharmacist dispensed a different ondansetron generic and it constipated her quite badly; we did not have a good time over Christmas.)
I think the trickiest part of managing chronic pancreatitis is found by many caregivers to be the identification of nutritionally appropriate foods that agree with the cat. It took me nine months to find a commercial food that Saoirse can tolerate and eat with little or no discomfort. Even that's not ideal because she has very early stage renal insufficiency and it's too high in phosphorus. Therefore, I have to give her binders. Sometimes the right food is the one a cat can eat.

Feeding smaller, more frequent meals helps a lot. Timed feeders are a great investment for kitties with pancreatitis. (I've used several and my hands-down favourite is the Petsafe 5.)
There is debate over how critical food fat content is for cats with pancreatitis. Some cats are very fat sensitive. I think others (like Saoirse) may be more sensitive to some fats than others. There is a Yahoo support group for feline pancreatitis. You'll need a Yahoo email account to join it.
@phlika29 (Sara) is a member and she says they're very helpful and knowledgeable. I think the consensus in that group is that less dietary fat is better for pancreatitis kitties.
There's a recent thread here on Feline Health with a good bit of practical information in the discussion. Here's the link:
http://www.felinediabetes.com/FDMB/threads/ben-has-pancreatitis.149407/
I would suggest getting regular labs done to monitor Archie's progress. Specifically I'd suggest getting a CBC and baseline panels for liver & kidney (both located close to pancreas), thyroid (pancreatitis can affect thyroid hormone levels), B12/folate levels (pancreatitis can lead to deficiencies) and, of course, periodic Spec fPL tests since the result is quantitative and may help to gauge effectiveness of treatment strategies.
In closing, there's an awful lot of trial and error working out a regimen that suits any particular cat. There's a lot of detective donkey work involved, too. I and others have found that any changes to diet or medication regimes need to be done slowly, and preferably only changing one thing at a time so that triggers might be less difficult to identify. Major flares can be awful - for caregiver as well as cat - so anything that reduces risk of same is a good plan. I keep a daily journal in Saoirse's spreadsheet. I have found it to be an invaluable aid in finding ways to manage her condtion (especially if I need to backtrack to something that worked better!). Be sure to study food labels thoroughly. Keep a log of any triggers that you may identify and try as best you can to avoid them.
Hope some of the above and the info on Ben's thread will be of assistance to you. Needless to say, any time you and Archie need help please post and let us know. There are several members here whose cats have pancreatitis problems.
Mogs
EDITED TO ADD:
Keep an eye on blood glucose levels, too. Granted Saoirse is diabetic and not all cats with pancreatitis have comorbid diabetes, but when Saoirse was receiving insulin her pancreatitis symptoms were significantly less, and they got worse again when insulin treatment was withdrawn. Other members here have reported similar observations in their cats. I wanted to put Saoirse back on an insulin maintenance program many months ago (once-a-day microdose with close BG monitoring) but could not get veterinary support for this treatment strategy. I had to watch her clinical signs deteriorate and for her BG levels to fall well out of regulation before I could get an Rx to start her back on Lantus. The first few weeks were shaky but she seems to be doing better now. I've been able to reduce her ondasetron dose and her need for bupe has diminished significantly since her numbers started returning to the tight regulation range in the last couple of days. For information, there is human research being done into the use of insulin in the treatment of acute pancreatitis. They have found evidence that insulin appears to have a protective effect on the pancreatic acinar cells. Here's a link to an article about the study:
Insulin offers new hope for the treatment of acute pancreatitis
.