It was over 16 years ago it happened to me at work. Not as bad as your experience. I reported to the council and they brought in a machine to check the office. So have your contacted the local council to see if they may help. Good luck
This time of year is classic for fleas to start re-emerging! Any eggs hiding in the carpets will start to hatch when the central heating goes on in the winter.
The larvae can survive for several months and Gilbert was right - movement, heat & moisture will reawaken them. I wonder if this might be what's happened in your case!
I would go to your local vets and ask for their most trusted household spray. Wash all bedding, curtains, sofa covers etc on a hot wash, and keep hoovering daily (spray out the Hoover too). You might need to repeat every few weeks, to completely clear the problem.
At the end of the spring, do one more house spray, just to clear any lingering tough nut eggs before the weather warms up.
I hope that helps!
(I'm a Vet Nurse, most of my consultations at this time of the year are flea related!)