£100/day is way too cheap for the domestic market; I wouldn’t do it for that & at that price your either going to get someone who’s new (but not necessarily bad), a real cowboy or someone whose desperate for work. A lot depends on location but the last two have an uncanny knack of going together, the best spreads can usually always get work.
Expect to pay at least £150 (£180 in Surrey) but you should get a top notch job for that; but the risk is always there so it’s important you check out their previous work.