a 21" barrel!? wow, I your going to have a hard time cleaning that with a fluffy
Looks like you have everything you need to get started, would suggest you get yourself a better hopper, something second hand like a halo, reloader b, vlocity, torque for around £60, those shake and shoot hoppers wont be able to keep up with the rate of fire that your finger pulls at.
I would suggest you perhaps stick to the 16" barrel, the standard length is a 14", it doesn't really effect accuracy i find, and the longer it is, the more 'in the way' it gets.
Get yourself a fibre wrapped Air tank, preferably a 68ci [cubic inch]/4500psi[pound per square inch] tank, make sure its got a good amount of life on it. Tanks have 'born' dates on them, specifying the year and month in which they were made, all fibre wrapped air tanks have a 5 year life before they have to be retested.
Steel tanks are far heavier, they are cheap, but I quickly grew out of using my air tank in my first 3 months of playing.
Get a bottle cover aswell, helps hold the bottle into your body, and you can just stick it in the wash afterwards to clean it
*Regarding the harness information I would recommend that you buy yourself a battle pack(i have one for sale if your intrested
), these hold the pots in which the paintballs are stored - 4+3+2 denotes how many pots the pack will be able to hold.
Get yourself some pots aswell with the battle pack. Best thing you can do is try the harness's available at the NSPL event on either the 16 or 17 May 2009 where there will be trade stands up with lots of shiney gear for you to look at.*
Depending on how much you get into paintball, you'll get along with what you have or you will quickly want to upgrade. What you have is a package that will last for now, its a very very basic package.
On another note, there is a major tournament happening this upcoming weekend at NSPL Reading, that you can turn up on koth [king of the hill] on the saturday:
http://www.kothpaintball.co.uk/
and the x-ball lite and all other divisions happening on sunday:
http://www.nspl.co.uk/index.php
Before you play any paintball, I would recommend hat you get some insurance from UKPSF at:
http://www.ukpsf.com/join.asp - Joining this will allow you to play at paintball site which will require you to have this membership, as well as the above tournaments
Hope this helps, get yourself down to some events, and see what its all about and happy shooting