On watch forums there are some bits of advice that are often repeated, but seemingly never without the specifics.

I often read people saying, oh a standard 2824 can be regulated to etc etc. I've a watch with a 2824 and it's typically +10s/d (and always has been) and I would quite fancy that being improved.

In London whereabouts would I be able to walk in and ask to have it regulated? And what kind of price range should I expect? (I'm not interested in it being sent it in the post) I work all over town so popping by would be unproblematic.