Try Zooplus.
(Link:
http://www.zooplus.co.uk/shop/small_.../hamster_cages )
The Barney cage is very reasonable, and meets the space requirements for a Syrian. The Alaska is also very good and brilliant price-wise, but not quite as good quality as the Barney.
There's also the Alexander, which is the bigger version of the Barney and is huge! That's quite expensive, but still well worth its price, if you have the budget.
With Zooplus it's worth waiting and watching the prices as they fluctuate quite a lot. The Barney is at £49.90 at the moment, but it often drops to £39.90 (which is the price I got my two for.
)
If your ham likes climbing, hammocks are a good idea to prevent him falling and hurting himself, and also gives him something to clamber on.