In my experience the job isn't that easy to pick up and put down. This is my third year as part time FI. In each summer (which seems to start in week 2 of July) I pick up 3-5 PPL students who I assume wouldn't be too pleased were I to ditch them for cosy days by the fire with the GF.
Tend to get them taking their tests by Easter, though this year there has been a slight technical hitch as I was temporarily unairworthy for a couple of months. The 'hungry' period has previously been April/May/June. Though as my students have stood by and waited that should be filled this year. Loyalty works both ways.
In any case, though the days are short you can get some really good weather in the winter. I think last year there was a 9/10 consecutive flying day period in December and I managed to do over 40 hrs P/T that month.
Seems to me that you've a couple of options:
1.Go part time in your current 'day' job, or swap it for another where you can be P/T.
2. Ditch the G/F and buy that caravan. You'll could well end up with a more understanding one when you're following your passion....
PF