Just spotted that Silverman's (http://www.silvermans.co.uk) have a "USA Hammock and Mossie Net" for about £35. They don't give much detail, but it looks like it might have a waterproof roof section so might be worth investigating.
I've recently used a cheap and cheerful combo of a British Army tarp and a cheap nylon mesh hammock that I bought for about £5 in an army surplus shop. It was not used in bad weather, this summer being what it was, but worked pretty well. It was worth cutting a couple of sticks to act as spreader bars on the hammock - it stopped me feeling trapped!
You probably want something less basic than this idea, but in a past military life, I've also used a couple of British Army ponchos clipped together to make a sort of low hammock that 2 people can sleep in, in relative comfort
. Clip the ponchos together like an envelope, tie the hoods closed to avoid leaks and suspend the lot a couple of inches off the ground. String up the hood of the top poncho to an overhanging branch to make a low tent/wigwam shape, and climb in. Your weight will make the base poncho sag onto the ground, but the edges will stay up in the air and keep water out. The poncho is waterproof so that's no problem and the old 58 pattern army sleeping bag had press studs on it to keep it in place in just this sort of set-up. It's a bit claustrophobic and would not be much fun in really wet weather, but if you want to move light and fast it could be an option.
Ted W
I've recently used a cheap and cheerful combo of a British Army tarp and a cheap nylon mesh hammock that I bought for about £5 in an army surplus shop. It was not used in bad weather, this summer being what it was, but worked pretty well. It was worth cutting a couple of sticks to act as spreader bars on the hammock - it stopped me feeling trapped!
You probably want something less basic than this idea, but in a past military life, I've also used a couple of British Army ponchos clipped together to make a sort of low hammock that 2 people can sleep in, in relative comfort

Ted W