A 3,000psi steel/aluminium cylinder at about £30/£40 will do just fine.
If you are flush on funds then consider a fibre 4,500psi cylinder, however this needs more thought and some hands on.
Firstly - is it worth an extra £100 for the extra capacity, will you be playing at sites that provide 4500psi fills?
There is a variety in shapes and sizes - you can go for a smaller compact cylinder, but end up with only the same amount of air as a normal 3000psi cylinder, or go for a bigger more bulky cylinder.
The right cylinder will ergonomicaly fit you.
Remember that a fibre cylinder costs more and should be considered an investment that will require hydro tests to get the 15 year life. A steel cylinder is much cheaper and though it can be tested is cheap enough to consider disposabable every 5 years.