Hi Unfit,
I use a automatic inflation lifejacket when shore angling. I use a Baltic, but there are a lots of good makes around. It's a 150 Newton lifejacket - newtons in this case being a measure of the bouyancy provided when fully inflated. The jacket is quite neat to wear and does not get in the way when casting, etc. It has a CO2 cylinder and firing mechanism that should inflate the jacket within 5 seconds of entering the water - that's the theory anyway

It also has a manual toggle that you can yank on in the event that the automatic system fails. As a last resort there is a mouthpiece that allows you to blow up the jacket.
A few tips from my own experience:
When you buy the life jacket, buy a spare re-arming kit and keep it in the car. This allows you to rearm the jacket if it goes off accidentally (dropped into a pool of water

for example).
Wear the crotch strap supplied. Otherwise there is a danger that it will come off over your head.
Follow manufacturers instructions regarding inspections, re -arming, lifetime, etc.
Treat it with the respect it deserves. Your life might depend on it one day. Don't throw it into the boot of the car and chuck a load of gear in on top of it.
Hope that helps!
Regards,
Liam.