You must discuss your situation with your accountant. This is a complete minefield and the inland revenue can just shift the goal posts as suits them.
Please, please take this to your accountant. I have been on the recieving end of an IR investigation when I was employed and doing freelance at the same time. They will tie you up in knots, never give you the same answer twice and eventually you will have nothing but hassle for years to come.
Do yourself a favour and put your finance in order now!