Newbie, meet guide section; guide section, meet newbie. 
This should get you started bud: http://306oc.co.uk/forum/thread-42.html It's a fairly good explanation, although the power estimations are a bit optimistic and "uprated" panel filters will munch your maf, particularly K&Ns it seems (you don't want that to happen btw). Actually, you can pretty much ignore the bit about induction, people are still using the standard airbox at stage 2 without apparent issue.
The MOT still only tests for smoke from diesels, and although a bad stage 1 map could cause you to fail on that front, removing the cat is certainly not an issue. I guess you know this since you mentioned a dummy-box, but i'll say it anyway in case - the exhaust must have at least one box in to pass an MOT. The centre-box is pretty much a straight-through design anyway, so you could use that as a back-box if you're on a budget, save some extra pennies towards a map.
Blanking the EGR isn't particularly difficult if you've done anything mechanical before, it's just that access isn't great. Ideally you want to get the thing completely mapped out as well, failing that you will have to disable the air-doser - if you have one. If you just unplug both items the ECU will log a silent fault, however this won't affect running much and won't directly trigger the EML.
This should get you started bud: http://306oc.co.uk/forum/thread-42.html It's a fairly good explanation, although the power estimations are a bit optimistic and "uprated" panel filters will munch your maf, particularly K&Ns it seems (you don't want that to happen btw). Actually, you can pretty much ignore the bit about induction, people are still using the standard airbox at stage 2 without apparent issue.The MOT still only tests for smoke from diesels, and although a bad stage 1 map could cause you to fail on that front, removing the cat is certainly not an issue. I guess you know this since you mentioned a dummy-box, but i'll say it anyway in case - the exhaust must have at least one box in to pass an MOT. The centre-box is pretty much a straight-through design anyway, so you could use that as a back-box if you're on a budget, save some extra pennies towards a map.
Blanking the EGR isn't particularly difficult if you've done anything mechanical before, it's just that access isn't great. Ideally you want to get the thing completely mapped out as well, failing that you will have to disable the air-doser - if you have one. If you just unplug both items the ECU will log a silent fault, however this won't affect running much and won't directly trigger the EML.