It's not just a UK thing, it's a Washington and LA thing as well. It's a very peculiar concept to me that so many people treat tattoos as a fashion accessory; the "I like this tattoo where they have it, and I want it just like that on me" (ignoring that this person is very possibly built and proportioned very differently than they are. It's fine, not really offensive, and not really my problem; it just seems a bit like they're forgetting that this isn't the must-have phone that they can just trade in after a better one comes out.
Its not rude to ask your tattooer for their rate. It is rude to ask various artists for prices on a design and price hunt. Show that you intent to get tattooed by the artist you want and ask for price once everything else is done.
I always ask how much the tattoo will be, but I do it last. If you hear artists complain, its from people who price hunt and dont really want a tattoo, they just want a deal.
Tattoo prices vary, based on so many different factors. Only the artist doing the tattoo can tell you how much a design will be.