Maybe not relevant to the OP's situation, but can I just mention that I started my PPL on 1st week October and passed my skills test before the end of April, a shade under six months. This was in the South East of England.
I guess what I am trying to say that it IS certainly possible to complete a PPL during the winter months in the UK, but you do need to have a flexible job and flexible approach to your flying. I booked several lessons per week, knowing that some would invariably be cancelled due to weather or technical issues.