i havent run pamper parties myself but helped out with crafts when my sister used to run them (im crb checked too)
as the other poster mentioned they can bring a good return and are fun .. to a point, lol
unfortunately my sister found them way too stressful and really hard work, and did her last one on sunday.
she couldnt cope with the packing, unpacking, checking all stuff she needed was in kit, double checking, then panicking when hello kitty tattoos stopped being produced etc etc
id say if you are super super organised, and dont let anything phase you go for it - tbh my sister is bit of a stress head, but i must admit i didnt envy her having to re-do the girls nails when they smudged them for 2nd time or threw a wobbler when they didnt like any of the glitter tats etc
having said that they were really popular think she pretty much had 1 booking a week and up to 3 during the holidays - try and theme them if you can, the following were really popular : hello kitty, funky chick (glitter tats, funky nails and hairbraids) and she also did a cath kidston themed manicure for the older girls age 12+ which was popular .. surprisingly disney princess wasnt popular at all and she stopped offering them altogether!
good luck if you decide to go ahead .. but take a deep breath before you enter those little divas houses with the unsuspecting balloons on the door lol
ps. one thing that the birthday girls loved was being involved in their own party .. whilst she was unpacking she used to get the girls to decorate name labels with themed stickers and write their friends names on them, then theyd stick them on the guests as they arrived. she also got the bday girl to run a lucky dip at the very end with a bobby pin attached to cpl business cards as prizes, she never mentioned this to the mums when they booked so nice little surprise .. and free advertising