Unless you manage to get a bulkhead seat with the extra leg room then stay away from them.
This is where the people with young children / babies will sit and if you want a better chance for a quieter doze on the plane, far away can be better.
Sitting near the toilets is great if you need to go but people will usually pool around that area as they tend to be near exit doors and have a habit of leaning on the back of the isle seats, very irritating if you are trying to sleep.
Isle seats I find are easier if the other people are not always in and out for a walk or the toilet but make sure you keep your legs clear of the isle or you are likely to get a trolly in the kneecap.
Singapore airlines are pretty good. Flown with them Standard and first class (long haul). First class is wonderful, worth the stretch from business class if you can make it. Standard to Busness class tends to be a big jump. I would stick to economy or prem economy for short haul.
Just taking a couple of sample dates, London to Singapore 25th Sep -> 17 Oct.
Standard: GBP 489
Business: GBP 3500
First: 5800
Singapore airlines also, as someone else mentioned, provides power for laptops etc for Standard (economy) class. No need to worry your laptop is going to run out watching movies. They also have the clamshell seats on the A380.
I tend to use the onboard video for stuff I have not yet seen, take a few movies and maybe a series or two (CSI or the like) on the laptop and have a good book so I can chop and change and not get too bored with one or the other.
Eva Airways was pretty good going to Thailand from London. They had the clamshell seats in prem economy.
I would advise staying away from BA for economy as my last couple of experiences with them were terrible.
As for the A380, I found the seats are pretty wedged in so not as great flying this plane as I expected. Business and first class should be pretty good.
RB