Wordpress back-end functionality help

I'm working on a site which is almost complete but I just need to add a certain piece of functionality. I am a) too busy to do it myself. b) too slow with this kind of thing to do it myself. It's all about self-populating forms from customers' details. Hopefully not too tricky for someone who knows a bit more than I do.

Strictly UK only, please. Quick response welcome as deadline looming!

Further work a very real possibility.

Thank you.