Where do you get them developed & at what price?
Until recently, I used a local printer for several years...print & Process of a 24 film costing £5-50. I had to find somewhere else because the bloke of the outfit kept cocking it up and the last time was the last straw. He chucked away most of the last film in it's casette and only developed a strip of four negs. Frantic search by one of the ladies discovered it in the bottom of the printing machine, and she carefully processed it. The bit that the bloke had developed was totally unusable, so it turned out to have been a blessing.
Now I go into Exeter and use a Truprint shop. And the prints are totally superb. Can't believe the difference. £5-99 a film, but I'd rather pay extra and get good negs and prints than crap stuff. The difference shows even more when you scan, as scanning picks up any covered-up mistakes and tweaking.
I've also got some envelopes to send away to Truprint, one of which I've just used to send off two films. I used to use them before the local printers and never had any problem. By post the cost is cheaper...£4 plus £1 p&p...and you can buy cheap film using the service. I ordered 5 for £5. £1 a film which is brill.
The larger Boots stores also do processing. I haven't used them but I've heard they aren't very good. Also by post, Bonus print. Look them up on-line and you can order envelopes (you can do that with Truprint too).
I personally wouldn't use Tesco as I've heard too many horror stories. For perfect results you'll need to be prepared to pay more, but it's worth it, imo, as you won't lose so much resolution when scanning...and they'll last almost indefinitely.
Sorry about the essay, but hope it helps!