Thanks all for the advice.
The cycle to work scheme doesn't open until march at the earliest so I'm going to stick with the heavy felt mountain bike with big apple tyres that I have already, it is a bit of a monster to heave uphill but is comfy and has very low gearing so gets me there in the end and I assume that once I have a little one on board I won't be in too much of a rush. As a few of you have said, it's not an expensive super bike that I really need, just something that hardy and it is that.
I've had it for so long that a few more months wont hurt before replacing it. When I do get the chance though I'm going to go for the Roadrat because I think that I will get a lot of enjoyment out of it but I will get a few of the added extras that will make it a bit of a trekker. I will probably get the most enjoyment from that one, it seems to fit my requirements well and has great reviews everywhere.
Thanks for all the help