Hi Sandy and Smartie, welcome to FDMB,
I'm in Surrey, so not too far from you.
Seconding what others have said here:
Yes, of course you can use a human glucose meter. Most of us do.

Here's a link to a page of info and pics about hometesting (I learned to test from this page).
http://www.sugarpet.net/bloodtst.html
And it's well worth trying to get onto the RVC's remission trial. But even if you don't get onto the trial you may still get some good advice from the main vet in the project (Ruth).
That 3 units is quite a high starting dose (but not at all unusual for a UK vet to prescribe that (my vet did the same)). It may be that Smartie
does need that amount, but really, the only way to tell is to test his blood glucose at home and see how that dose is working in his body.
For those willing/able to test we suggest that - as a minimum - the blood glucose is tested immediately prior to each insulin shot. That is so we have some assurance that it is actually OK to give that shot. And we generally recommend that
(for those new to dealing with feline diabetes) no shot is given if the pre-shot blood glucose is below 11 (or 200 in the US).
Other tests done during the insulin cycle help us work out the pattern of how the insulin is working in the cat's body. Most importantly, a test done at the peak of the insulin cycle will let us know how low the blood glucose is dropping. But other useful things to know are; when the insulin starts working (onset), and how long the insulin lasts in the cat's body (duration). It's also helpful to see how
fast the blood glucose is dropping. Cats generally metabolise insulin around twice as fast as humans do.
Caninsulin often has quite a short duration, and only lasts about 8-10 hours in many cats. And it can also drop the blood glucose quite fast in the first few hours. For this reason it can be helpful to feed a snack about an hour or two after the shot. That food can help to slow the drop.
You
may see that the peak of the cycle is around 4.5 to 5 hours after the shot (what we call +4.5 to +5) and after that the blood glucose will rise. It
may rise more steeply around 8-10 hours after the shot.
In some cats Caninsulin does have a longer duration and there are cats here who have done well on it (with some even going into remission). But it doesn't suit every cat. And if turns out that it doesn't suit Smartie then, under that is called the 'cascade system', you should have the right to ask for a different insulin. Some vets are very willing to help. Some aren't. There is no consistency in this regard!
It is a good idea to check a kitty's pee for ketones. Does Smartie use a litter tray? (it's harder to catch the pee of an outside cat!) You may well have some Ketostix or Ketodiastix on hand given that you are diabetic? There are some good pee-catching tips on this page:
http://www.sugarpet.net/urine.html
Please ask any and all questions you want to, we're here to help. And you may find that you get 'more eyes' on your posts if you post questions in the main feline health forum.
Welcome aboard!
Eliz