go to a local recycling place (used to be called the council dump) buy a 4.5 or 7k calor gas bottle ,then take it to a camping shop ,decide which size calor bottle suits you then buy a refill (swapping your empty for the filled one) and buythe regulator for that bottle + hose if you need it.this way avoids the high price of "renting" a bottle from new.
OK - so you can either buy a new cylender full of gas, or blag an empty cylender from a car boot sale, council recylcleing depot or ask your mates at work and get it re-filled.
A new full cylender will cost about £35 or if you can blag one it cost £12-13 to re-fill them.
Go to http://www.campingaz.com/ and on the top right of the screen you will see a link to where you can get them re-filled
BTW - 904 will also fit - just a smaller cylender but about the same price to re-fill it
Did the cooker come with a regulator? If it didn't, then you can look for either a Campingaz 907 bottle or a calor gas bottle, whichever one you can get for free or cheap Then you can buy the appropriate regulator for that type of gas.
Calor gas is cheaper than Campingaz; both are widely available in this country; Campingaz is available in France & Spain, but not calor gas.
Amazing family weekend with old steam engines, classic car displays, market stalls, and full catering and bar. And camping on site - Save £25 by booking in advance.