I've been living in my van for a few years now but recently updated my voting details to my father's address. Now the council are asking where I live. I'm no fixed abode and don't know what to say to them.
Generally when you register to vote from a 'fixed address' your address and details are added to the 'Electoral Role'. This enables the Council Authorities to send you the necessary voting documentation for both Local and National Elections. However, be aware that if Iyou use your fathers address, and he is the sole 'official' resident at that address he will be paying a reduced rate of 'Council Tax', so if you use that address and do not tell them your circumstances, they 'may' assume that you are living there and remove his 'reduced rate'. So make sure that you have it in writing (Letter or Email) confirming that you are not actually residing at that address but using it as simply a 'Contact Address', which of course is quite legal.
I generally find that if you explain your circumstances to 'officialdom' then there are no issues It is only when people are trying to do things 'under the radar' as some refer to it, that problems arise. So, if you really feel the need to want to use your legal right to vote (Which of course you do not have to) then I would suggest perhaps going in person, or writing, to the appropriate person, at the local Council Offices and explain your situation.
Good luck and please let us know how you get on as I am sure, with more and more starting to live more nomadic lifestyles, that this question may arise more frequently and it is good to be able to refer to a question accurately than theoretically