Some are nearly £1000! 
Do you have a John Lewis near you? I know that might sound nuts if you're trying to save money, but our buggy broke four times, and every time they gave us a great quality courtesy buggy, no questions asked while they fixed it (and were nice to us!). It meant it was only a minor annoyance rather than a total disaster.
Compare that to the recent debacle when a mumsnetter tried to get Mothercare to do something about her broken pushchair. They were rude to her and worse than useless, leaving her with no buggy - see this thread.
We spend about £200 on ours and it lasted about a year and a half (with repairs). We recently got our next one from a cheap shop (I got railroaded into it - don't ask! 
) for £80 on special offer. 4 weeks later and it's so broken it's unusable! DP is going to try to take it back today. keeping my fingers crossed but I'll be absolutely amazed if he comes away with a courtesy McLarren (sp?) or even a promise to fix/replace it without a lot of argument!
The prices might seem mental, but it's something you'll be using a lot, and you'll get to know it's weaknesses very quickly! A good buggy does make life a lot easier.
One way to save money we found was to buy a separate car seat. You can't leave a baby in the carry-bit that comes with a travel system for long anyway (not good for their backs). We got one instead that had a detachable crib bit for when DS was small. This doubled up as a kind of moses basket and worked well for us. I t didn't matter that you had to take it off the buggy because often DS was asleep in it and it was a good way to carry him about without waking him up. When he got bigger it worked as a push chair without the crib bit.
Also have you thought about a sling? I didn't come to these until quite late, and I wish I'd found them earlier. In fact you probably don't even need a buggy at first if you've got a sling. For a lot of journeys (e.g. anything with stairs) they're much less faff than a buggy. Plus having your baby close to you helps to regulate his / her breathing, and it's lovely to have your baby close and snuggly to you. I'd recommend the wrap around ones best, or an ergo-baby (avoid the baby-bjorn types. Although very popular they're not ergonomically designed, and not as good at distributing weight so not as good - or comfortable - for you or your baby).
HTH
"May just nick a shopping trolley and line it." Like it