I have joint problems which restrict what I can use - I have to think of what I'm likely to be able to do in the next few years rather than what I can do now. I have an ancient Toshiba Satellite 450 that I love but it's just too heavy for me. I dislocate my wrist just by picking it up. I need something as light as possible while still having the features I want.
Main uses will be to surf the internet, edit documents, email, view & upload personal photos (plus basic editing - not photoshop-quality), upload/download and play videos and photos (I have family living abroad), burn DVDs and CDs. I also play simple computer games - Tower Defence, Mahjong, Plants vs Zombies, I don't think I need any special requirements for those!
I know I can get an external drive for the DVD/CD burning so again, that's not particularly an issue. I also own two external drives so memory isn't that much of an issue either.
I do need a fair-sized screen - my current one is 15" and I don't really want to go any smaller.
I've tried a tablet but I don't like them - I want the functionality of a proper laptop.
I went to PCWorld (yes I know they're shite) but got a 'Have a look round'. And they couldn't put the batteries on the laptops so I could try picking them up. My fault entirely for thinking they could help. 
Any advice?