If you are building a kit plane in the UK, there are certain rules and regulations to follow.
Pick an inspector. He will visit about 5 times during the build, and offer advice should you need it. There's a list on the BMAA website (click here), you can get contact details through the BMAA. The first visit will be before you have started building - he will check the quality of the kit, and the proposed workshop to make sure you don't run into problems later. I asked John Hamer to be my inspector - as chief pilot for the BMAA, inspector for the Escapade during its approval process, and recently awarded the Royal Aero Club (RAeC) Certificate of Merit for his test pilot work, I could not get anyone better.
Form AW022 "Details of homebuilt aircraft project" is here. This needs to go off to the BMAA with a registration fee (currently £30). The kit supplier should have given you a certificate of conformity, which basically states that the kit you have been sold is the same as the kit that was approved by the BMAA in the first place. I sent a colour photocopy, and in fact, I photocopied everything I sent them.
CAA registration. Use this form and follow the guidelines. In-sequence registrations cost £50 - call to find out which ones are available. Out of sequence ones add a further £150 to the bill. An aircraft is only 'named' once and the registration letters cannot be changed afterwards.
There will be more paperwork for the BMAA later on (watch this space).