Firstly...go to a tourny and see waht other people are using..etc.
Play some supair before investing, in case it isnt your thing.
Where in London?
We (generally) reffer to Guns as "Markers", as it draws them away from teh whole, boy soldier, playing war in teh woods thing and is much easier on you at airports.
Markers come in different shapes and sizes, and certainly price ranges.
Top end markers, are any of teh following and mayeb a few more:
Angel's-
Made by WDP in Birmingham, very high spec, stuffed with technology. WDP liek to bring out several guns, not much different from teh last, every year.
They usually have a Flagship all singing all dancing model, and a lesser, but just as fast etc, plainer model..and then custom versions of each...hence...new Angels are worth sod all within a few months.
Timmy's-
Made in America, by Bob long. Full name "Intimidator"
Not fantastic build quality but very fast. Newer markers are better than the older ones. Very individual styling, some people swear by them.
Shocker-
Made by Smart Parts in America.
Smart Parts are a bit...unsportsman like, shall we say...but teh Shocker, is a pretty good, light marker that is easy to shoot and fairly easy to maintain, as is their other marker, teh ION, which is so popular its ridiculous, and is so cheap, it has killed teh secondhand market for markers.
Ego-
Made by Planet Eclipse in Manchester.
Similar in design to the Timmy, but so much better its untrue. Better build, better looking,. lighter, sexier, doesnt bounce like a rubber ball...a very, very good bit of kit. Pretty efficient and very little to go wrong.
DM4,5,C,6-
Made in America by DYE.
A Remodelled version of teh original Matrix...excellent build quality and reliablity (DM6 is tempremental at teh moment, some ironing to do!)...very fast, bit gas hungry but that can be improved, very gentle on paint, liht (DM4 isnt as light)...again, a very very good marker.
Theres loads of others!
Hoppers-
Most popular hoppers at teh moment are the HALO, Reloader B and Eggy.
The HALO is a force feed loader, that has eyes to detect thepresence of a ball in teh feedneck, and a motor to force the balls into teh gun at anywhere from 20-30 balls per second.
Pretty strong, but a bitch to clean with stock shells.
The Reloader B, looks teh same as a HALO, but uses sound to know when to feed paint, rather than EYES.
The Eggy, or Vieloader Evolution2, looks like an Egg.
Pretty reliable, not force feed but can manage 16-20 bps...reliabel but shells and lids break consistently. Good backup to a HALO.
Air-
Comes in 3 flavours, high, low and adjustable.
High has an output of 850 PSI and Low has an putput of 450 PSI (or there abouts) adjustable is just that, and can range from 200-1200 psi.
This part is controlled by teh regulator which sits on top of the actual bottle.
The bottle, usually will be fibre wrapped (looks a bit liek grey marble) and commonly can store air at 4500 PSI. 3000psi ones are still available, but are usually steel and heavier.
Also come in sizes from 0.8, 1.1, 1.5 and 1.9 litres...tho 1.1 and and 1.5 are teh most common.
I have to go top work ages ago!!!