As much as I hate using both, DEET and Permethrin (for clothing only) are about the only prevention methods I know of. After hiking off-season (aka tick season), I dump my clothes in the washer immediately when I get home (it's in the garage) and take an as-hot-as-I-can-stand-it bath to kill whatever ticks or chiggers are still hanging in there. Of course, that only works for day hikes.
I found this webpage of interest, seems they have the same problem in the UK, too!
http://www.tickpreventionweek.org/topten/