Discuss it with your chosen artist if you have one. If he/she is unwilling to design something for/with you seriously consider if he/she is the right person for you. If he is only willing to do whats on the wall or in a book, how good an artist do you think he is. If you do take a design along i would expect the artist to take it away, probably improve on it and at least alter it so that it fits/suits the shape of your body. Like all good artists, a good tattooist will want to create something, not copy any old thing.
Don’t be afraid to travel either, an extra £50 petrol money is worth it if theres no one local that you’re happy with.
Blimey, just re-read that and it sounds a bit preachy, sorry, just hate seeing people with average work when they could have something great.