Be VERY careful about doing wedding photography. There's far more to it than just having a big camera.
In argos your options are limited.
The ability to take fantastic pictures is more down to you than your camera.
Since you want to take a large variety of subjects, I would spend more on lenses than on a body.
for bodies, I'd be looking at:
nikon D5000
canon 500D
canon 450D
maybe nikon D90, but that doesn't leave you with much cash for extra lenses.
For lenses:
perhaps an 85mm f/1.8
50mm f/1.8 for portraits(this will be manual focus only with nikon unless you get a D90)
18-55mm will do for landscapes. (if it's a canon make sure it's the IS version, it's sharper)
sigma 70-300. OK quality, does reasonably close focusing.
If you go canon, I'd maybe go for a cheaper body and a 70-200mm f/4L, it's got unbeatable value as a general zoom.
To be honest, if I was going to be doing weddings, I'd want much better stuff than that.
something full frame for high ISO (like a 5D or D700) and a fast lens (something like a 70-200mm f/2.8)
Really you need to try out some camera bodies.
Go to a jessops or somewhere and have a good look at a couple of camera bodies, and pick the one that feels best in your hands.
To be honest, I'm quite put off by looking through argos's online catalogue of photography equipment.
They have several lenses listed twice under slightly different names and with slightly different prices. They're still selling the old canon 100-300 new. They list the SB-400 as just 'nikon flash gun'.
Also the prices are awful. They're selling a 24-105mm f/4L for £1079 on 'special offer'. Warehouseexpress are selling it for £799
Personally, I'd go with canon because i prefer their ergonomics/ button layout. BUT that's a very personal preference. You might prefer nikon.
Oh and one more thing.
Ignore anyone who just says something like 'get a nikon' or 'get a canon'. If they can't give at least one valid reason for that opinion, don't pay attention to it.
