I did what I should have done in the first place - I went to see Tim Pugh.
When I'd explained what I wanted, he got a couple of quotes together in a very short time, and I chose which one I wanted to go for. They don't carry a big stock in the shop on the Pavement, so everyone who comes in gets a "tailormade" solution.
Yesterday, Tim Pugh came round and installed the new laptop, and made sure it could talk to my desktop and printer.
And last night I took it upstairs so I could type in bed! On a tray, which was the Top Tip from Dale at Keeper's Pocket - he'd made the mistake of using a laptop on top of something fluffy that clogged it up.
It was a little bit more expensive than I'd thought, but it was well worth it for the peace of mind, and having someone who knows what they're doing and can explain it in layman's language to do all the technical stuff.