Try not to forget that you will get bad weather in the UK at any time of the year. I have found Winter to be ok for flying. You can come across some beautifully still crisp days with no haze, so don't give up hope yet! Also, you should absolutely be cracking on with the exams. Get them out of the way sooner rather than later.
In terms of keeping current, you mention that you work full time and only the weekends suit you. What about evenings either during the week or at weekends? Sometimes the weather can improve and you get some nice night flying. A night rating is 5 hours and
AFAIK this 5 hours can be included in the 45 required for PPL issue so its not wasted. Obvious advantage is that when you do get your licence it will not have the Daytime only restriction. Downsides could be more expensive rates for Instructor or paying extra to keep the airport running after dark. Food for thought.
Ryan