You poor thing, that is awful. You'll be laughing next winter with your new boiler though, and you'll soon have the house clean. Urghh, it's horrible though. I remember nearly throwing up when I removed the chrome sink plugs the first time when we moved here. I doubt the previous owners had ever cleaned them, and 5 years of sink gunk is not a pretty sight.
It sounds like you have a big flea infestation, the only solution is regular treatments, as unfortunately as most flea sprays and powders will only kill the adults, leaving the eggs and larvae happily developing. The life cycle can range from a couple of weeks to longer, depending on how favourable the conditions are. So rather like head lice, you have to do it regularly to get all the adults as they develop from the eggs/larvae.
I'd try a steam cleaner for the carpets too, you can hire them fairly cheaply, I've noticed you can hire them through my local Co-op.
You have my sympathies - the temptation to have a consignment of rats, tarantulas and a lorryload of manure delivered to their new address must be almost irresistable, but The Manks and their Manky pets are not worth it.
There will come a day when you'll love your clean, flea-free home, and be able to laugh about it. In the meantime, I recommend lots of 
, Anthisan and Afterbite for the horrible itching.
By the way, the best way to deal with a flea if you see one is to pinch them between your thumb and forefinger and push them down into a glass of water - as the little sods will even leap from the surface. Watch them swim till they drown. It's rather satisfying when they stop moving!