First of all, welcome! Second, does it always rain in London? Third, if you bring up your concerns about placement and adding on with more tattoos in the future to your tattooer, they should be more than capable of pointing you in the right direction. Part of a competent tattooers job is to use the space on your body well. They should be able to help you place things in preperation of additional work.
Welcome to LST. Take a look around at all the awesomeness and keep us update on your new tattoo!