Sarah, thought you might want to look at this thread

My Strider Story....... - BellyBelly Forums ~ Pregnancy, Birth & Baby

I had a similar list of requirements, but didn't worry about what sort of surface we would be walking on. It wheels very well on footpaths etc, and I've had no troubles on grass. It's four wheeler and doesn't have pump up tyres, so you wouldn't want to do too much cross country with it IYKWIM. Oh BTW, I have a Silver Cross Linear and I love it! It is kind of big, but manoeuvers very easily and nicely, and I don't think it's heavy. One of my big things was not wanting a three wheeler, so I was really happy to find this. I think it's much nicer to push than alot of three wheelers too. It's great for a newborn, but I haven't gotten further than six months yet LOL.

I was also looking at the Steelcraft prams, but now some of the girls on here have put me off them.

Oh, have you looked at the Valco four wheeler? I know someone with one, she loves it!