Hi,
Personally i'd go with a male hamster. Mice usually stink especially males and they tend to be skittish. If you get a syrian hamster you can only have one on its own as they are territorial. Dwarf hamsters can be kept in pairs but i'm not too keen on them as mine was a nippy little thing. The reason i said male is that i have had loads of hamsters over the years and males seem to be a lot more laid back.
Personally if i was looking to get a new furrie, i'd go for rats cos they are great. A pair of rats are the best small pet you can get. They can be trained to come when you call them. You wouldn't be able to get a decent cage though for £30 unless you went second hand. I had mine in an indoor rabbit cage which is 4 ft long as they like lots of space and toys.
Emma
OMG NO GERBILS! I had a pair of Gerbils and they were evil. I prefered my one teddybear hamster over the Gerbil anyday. The only good thing they have is that there more active than hamsters. But hamsters are way friendlier.If possible I would go with gerbils. They don't smell like mice but are as active and they are always ready to play unlike grumpy hamsters. I know you hadn't thought about them but maybe you should. They are very unlikely to bite and the most interesting rodents to watch and play with but that is just my opinion.