I would like to know whether it is acceptable to have any part of the car over the lines. For example, is it ok provided your wheels are not on the double yellows?
No - it is not acceptable to have any part of the wheels on the yellow lines, not sure if your boot or bonnet can hang over a little (I assume that this is ok) but your wheels or any part in between the wheels must not hang over or touch
There are 2 main get out clauses for parking tickets on double yellow lines:-
1) The double yellow lines MUST be closed at the end i.e. a yellow line across joining the 2 ends of the double yellow lines together
2) There must NOT be a break in either yellow line in any part of where they are i.e. if the double yellow lines span 1 mile of road and you park at one end and at the other end there is a break in one of the lines then any ticket you get is non enforceable
If either of the above occurs take a picture of the break or the lines not closed off and that is your defense for not paying the ticket - any judge should throw the case out of court and blame the police/council for wasting their time