Please take my word for it and complete a Form P85. This could save you endless trouble in the long term. I have known of cases where the taxman has said individuals are non resident and then denied the position because this form was not submitted, screaming, shouting and demanding back tax, interest and levying penalties, As I said, belt and braces. You hope they will not be interested in your world wide income until some twerp in HMRC notices the lack of a P85 and comes down on you like a ton of bricks. I have been at a meeting with the Inland Revenue as it was then where a tax inspector was produced who demanded the immediate settlement in cash of tax which was not even due. Needless to say he did not get it, merely reported to his superiors, and the company received an apology from the Head of the Office concerned almost by return of post.
The rules for Class 2 NI are relatively simple. The Gov UK Web Site advise:
'Class 2 - but only if you worked in the UK immediately before leaving, and you’ve previously lived in the UK for 3 years in a row or paid 3 years’ National Insurance'
If you do not conform you may be pouring money down the drain, so be a tad careful.
As for licence verses tenancy, correct. The LCC used to let advertising hoardings by licence and every now and then would have trouble with big boys invoking the Landlord and Tenant Act, 1954. After a bit the penny dropped as the Council declined to let space for vacant sites which in the long term were due for redevelopment. The regular 'Arthur Daleies' of the area were a better proposition. If you asked them to go they were off in a flash!.