Ok, sorry... It's a Hybrid, didn't make that clear at all. Anyway, I after pumping up the tyres went flat again on my way home. They DO have valves - they are the larger of the common type (if that makes sense...). When I tried to remove the outer tyre to get to the inner tube.... well, there just wasn't one. Difficult to explain but the two 'ends' of the tyre were not 'ends' but met in the middle and I wasn't even able to remove it from the wheel frame, whereas I'm sure it shouldn't be that hard to do normally. Oh, and I went to a bike shop today to get a puncture repair kit, will undoubtedly have to go back tomorrow, but just wanted to know if there was actually anything I could do myself. Thanks