Well Tony Blair once washed my car....
Nah he didn't really, would be a great story though wouldn't it?
I haven't had much to do with any MPs although met one or two prospective ones when I was involved as a Poll Clerk and counter for the council a few years back. Mostly trying to pester us during the count!
My parents have dealt with their local MP a few times over the years and tried to get things changed as my mum is disabled. They haven't had a huge amount of luck although I think a couple of drop kerbs got put in eventually. They also got invited to join a committee that oversee changes locally for disabled people, but I guess that's more of a council thing. I haven't had much cause to contact mine, although there is a drop kerb issue near us so maybe I'll get pestering!