You ask an open ended question.
Yes, I now realise that, having spent a couple of hours looking around!
Last time I purchased a laptop (as part of my job, where brand etc are dictated to you before you start picking a model) there were only "laptops" - none of this "desktop replacement laptop" or "netbooks" etc etc... I clearly need to make that decision first! The old laptop was only really used for internet surfing, primarily because that was about all it could handle. So whilst a netbook seems an obvious choice, budget seems to allow for something much better and you never know, I might get into this PC-based music thing after all! 
As for the vouchers, that is "just the way they do it" (not a direct quote) - I believe it is common in the industry. Insurance company approves the claim, passes it on to another company who find a current model that matches the spec of the original laptop, and bases the amount of the settlement on the value of that. Which, in insurance parlance, is what they call "like for like" replacement. It would have been nice to have the cash, or at least not be restricted to Comet, but I'm not too fussed - the old laptop really was on it's last legs anyway.
No personal experience with buying laptops
but I have built a few pc's. The best advice I can give is to get the
fastest processor you can find with the biggest amount of memory your
budget allows. If you want to play games then look for a half decent
dedicated graphics card as well, 256mb gfx card as a minimum.
Just had a look on Comet website and spotted this,
£100 off but it's still £50 over budget it does have the fastest
processor and the most memory (4 Gb) at that price point though plus
320Gb hardrive. Also has a decent dedicated graphics card if you wanted
to play games on it, dvd burner and it also plays Blu-Rays and has an
HDMI out. It says on the product info that there is a windows 7 upgrade
option, don't know if this is a free upgrade though. Looking at some of
the cheaper laptop specs I would say that it would be £50 well spent
over the others at £600
Cheers - that does look pretty good and I do like the idea of an HDMI out. Have heard the "Acer" name quite a lot, but never actually seen or used one.
Panasonic TX-32LXD70; Sonneteer Byron CDP, Pro-ject Debut MkI, Pioneer BDP-320; Onix OA32LE, Onkyo 876, CA640P; Speakers: Ruark LCR, MS-302 rear, REL Strata 5