Hi,
I got my daughter's done at a shop on Northcote Rd, I cannot think of the name of it, which is not very helpful

BUT it is a small shop near to Fat Face, sells a lot of photo frames... Will look at the name tomorrow if I remember.
ANYWAY, they lie the baby on a piece of white paper on the floor, so not ideal, (my daughter was 8 mths at the time), but they got the job done fine...I guess you could take a while/light blanket for the baby to lie on if you are worried about the hard floor. Not the best place I imagine, but was fine, only took a few seconds.
Hope this helps a bit, will try and find out the name!
A x