Looking at the housing page you can also put about 10 camcorders in the housing .. so if an accident does happen you will be able to replace camera easily. That will come out quite a bit opver budget.
There are changes between each camera, so the camera needs to be specified prior to ordering the housing. My guess is they can be retrofitted if you do need to get a different camera. A couple I mention below can be retrofitted and/or used with more cameras. (I have an old Gates housing that takes any TRV camera just about, man I wish all the other equipment worked like this :D )
the Ikelites dons’t come out much cheaper than everything else from what i can see ..
A bit cheaper, the housings can be had for around $500-$650 (at least in the U.S.)and some of the Canons have been on sale for about $300 or so US (same for the Sonys)
Gates, L&M, Amphico, Sea & Sea, Top Dawg (Top Dawg II is another housing for $900 which handles many cameras http://www.topdawgvideo.com/compatibility.htm , so maybe still gets under 1,000 pounds with camera) and some others make nice things, but usually more expensive, and often you need extras such as monitors (more so for the electronic ones, many mechanicals ones have areas to see the screen, such as the Gates very often, or reversing mirrors like on the Iklelites)
BUT I just remembered something for the original poster. (trouble is most of the stuff I know is U.S. side)
http://www.dive-equinox.com/freecamera.html
Housing and Canon Camera for under $1000 US, with Sony a bit over $1000, but I think it comes in under 1,000 pounds These housings can be retrofitted for many other models. Equinox is good to speak with also, very helpful.
Yeah the Ikes are not very pretty, but they work. I am in that great debate right now for a new U/W video housing. Can get the Ikelite and use my old WA lens on it for about $1300 U.S. or get the Gates with a WA Port for about $2800, but the Gates is smaller and cooler looking. And I really do like Gates housings (I may have mentioned that I think :D )
EDIT whoops had to change euros to pounds