I can answer some of those. My 12 mnth old son is on a pump - diagnosed 4 weeks ago.
1. Can you choose which pump you have on the NHS?
No, I was told which one it was. But to be honest, looking at some of the other pumps available, they are all very similar. Your PCT might let you choose though.
2. Does a pump only deliver bolus insulin?
No, it does basal and bolus. You can set the basal rate to be different every half hour of the day on the pump we have. Very controllable.
3. How hard is it to get the hang of working the thing? Do the diabetes 'specialists' train you?
I got a 2 hour training session with DN a great instruction booklet, and lots of help over the phone. They are not that difficult to work out and I got the hang of it very easily. It is very similar to mobile phone menus. The problems/nervousness I had was with loading the reservoir and putting the infusion set in (but I'm putting it on a baby, so it's a bit more stressful!)
4. Do you have to wear it at night and if so, does the tube get tangled/pulled out often?
Yes you have to wear it 24/7 unless you disconnect for a bath/shower/swimming. You can top up insulin when you reconnect up if you've been disconnected for a while. Tangled - not really, my baby is very active, and he has a bum-belt carrier. It's never pulled out because the infusion sets are very strong, and it's even dangled and pulled and still not got pulled out.
Overall, I would recommend at least trying one. The pumps are brilliant IMO - my son can pretty much eat what he wants when he wants, and I can give him tiny amounts of insulin to match what he has eaten (for example 0.1 of a unit). His basal rates change 4/5 times a day - he's on tiny amounts during the night (0.075 of a unit per hour) and 0.2 during the day with a few other tiers in there. Go for it.