Can't be arsed hunting down the you tubes but there are some under rated UK horrors (to offset the terrible low budget efforts with Danny Dyer and his mockney mates) beyond the usual 28 days later etc.
Eden Lake - chav kids mess up Michael fassbenders romantic weekend plans, Cyp already mentioned
The children - evil posh kids ruin Xmas for everyone
The descent - technically a UK film
Cherry hill lane - chavs again