with the green's one mate, it bolts straight on, i say bolts. You remove the rocker cover (spelling), which houses the air filter. Then the green filter will simply go over the intake hole at the back, quite a large bore size. jubilee clip it.
Then a breather filter which comes with the kit will jubilee clip to the breather hose (or vacuum can never remember which ones which, the left hand one anyway.
The breather or vacuum hose going from the top of the engine runs back to the filter itself.
The kit was around 75 from halfords came with everything. You will need to go up to the counter and special order though.
Gives a lovely sound as well!
Have an engine bay pic if you'd like...