Hi Duncan, I moved to a gas one a few years ago and never looked back the convenience did it for me too, light up and cooking within 5 minutes, plus control of the heat.
I use Calor on mine so bought a blue regulator and a large gas bottle lasts for ages
I have an Outback which is a recognised quality make and you can normally get spares for them too, Webber is also a top make
The garden centre at Gailey Island , Dobbies i think , used to have a good selection but are a bit pricey.
There is a place in Welshpool called Charlie's or the Welsh equivalent is Coed y Dynas, they have some really good priced Outbacks on offer at present , a bit of a jaunt but they have a website so you could probably see the choice on there. - just checked and out of stock of one at Â£129.99 !
I always make sure that I get one with a warming tray which is usually fixed in the lid, it helps take stuff of the heat when you need to or will just store it and keep it warn until needed, then its just a question of size depending on how many people you may feed from it.
Argos have one on offer depending how much you want to spendhttp://www.argos.co.uk/static/Product/p ... 430763.htm
I have bought many BBQs over the years and hope the above helps a bit