For sites near manchester I know only of Northern Quarter which is sup air. If you go to Northern Quarter then pack only what you need as there is a hill you have to walk down to get to the site and then walk up at the end of the day. If it has recently rained the hill will be moody and rolling your kit bag up and down it will leave it looking ver messy! I would recommend trying to go to Northern Quarter so that you can get a good idea of what sup air is like and at £15 you don't have to rob the local Post Office. You can use your air systems there by the way.
If you are willing to travel a little. There is a good woodsball site near southport -
frontlinepaintball.co.uk
That is a Woodsball site that also will let you use your own marker and your own air or CO2 depending on whatever you want to use. There is a walk on there on the first sunday of every month except January (as everyone has empty pockets after christmas). Everybody is nice and friendly there.
What I strongly reccommend doing is getting a 2nd hand ion with a few upgrades (look for ASA, an upgraded feedneck and an upgraded barrel), a
2nd hand decent hopper (egg/halo/empire), a 2nd hand mask (you live in manchester so get to
www.planeteclipse.com , theres a post code on the website, put the post code into aa route finder along with your post code and print off the directions. It isn't that far away from the trafford centre. When you get there have a feel of the ion to see if you like it however, the main reson for going will be to try on every mask they have as whch mask you like best is almost a complete personal choice), and a 2nd hand air system (try get 3000 psi with a few years left before it needs a test or you could buy new for about 50/60 £)
Try and buy 2nd hand as it will be almost certainly be good quality items you buy and you will save alot of money.
your looking at 2nd prices of about:
ion : around 90 depending on the upgrades and quality/age/amount of use.
hopper : 30-60 depending on which one you want and the quality/age/amount of use/make .
3000 psi air bottle : about 20-40 depending on quality/age/amount of use/how long left before it needs a test.
mask : 20-40 for a decent one depending on the quality/age/amount of use/make.
You could probably find a package deal of all these items which would save evan more money if you waited a little bit for it (maybe a week or less).
Once you have this kit try Frontline and Northern Quarter to see what you like best. The ion will be ok in the woodsball and ideal for sup air. And because you have bought a 2nd hand ion if you decide you want the Tippman you can sell the ion without loseing much/any money.
Have fun!