You can buy DIY Wills from most good stationers, Aldaniti, then follow the instructions as per Redhead. Even if you don't own a house, property counts as a bike or a car, even furnishings, kitchen equipment, etc. If you think nobody would want any of that, you could stipulate it be sold and the proceeds given to Mrs Bloggs, or donated to the charity of your choice.
If you have a pet, you might want to stipulate to whom the pet should be entrusted, and perhaps leave a bit of money to them to help care for it. Don't know if you have a horse, but, if you do, you might think to ask any horsey friends if they'd like him when you've passed. I put in my Will that Songsheet was to inherit my half of the mares and foals I had, plus £1000 towards their keep, for example. That sets your mind at rest about Mr Tinkles or whoever!