The CAA rules and the coronavirus legislation dont join up. Clearly if the aircraft is used for work - either for any individual to get to work or to undertake allowed commercial purposes - then it is lawful to move the aircraft for maintenance.
However, if an aircraft is only used for recreational purposes, or indeed for other purposes such as training which are prohibited, the Act does not allow you to leave your home to move the aircraft because it isnt essential. You could just as well wait with the maintenance overdue until the Act lapses and then get approval from your maintenance organisation to move it.
I suppose a CPL who is employed to move the aircraft by the maintenance organisation is legal as both the maintenance can continue and the CPL is 'working' and cannot work from home, but there is nothing I can see that allows a private pilot or indeed a commercial pilot not legally employed for the flight to move an aircraft otherwise.....