Could we have fleas?

[Teapot101]

We're all getting bites, me a couple but my DS and DD quite a few. It seems to be overnight but the animals are not allowed upstairs although they leg it up occasionally. We have 3 dogs and 2 cats. I haven't seen any of them scratching. Just seems an odd time of year to be getting bitten. They are due a flea treatment, will do ASAP.

Yes, could be. Check the animals with a coat brushing on a white surface - bath works well, or onto kitchen paper. Look for black comma shape specks that turn red if you wet them (flea dirt). It doesn't matter if the animals are not allowed in certain areas, flea eggs are sticky and get carried around on people's feet. Treat them all with something decent (not frontline or anything from a pet shop) and a tapewormer, and treat the house and car with a spray containing permethrin and an insect growth regulator e.g. RIP, Indorex, Nuvan Staykill.
You need the little buggers to hatch before you spray, so hoover first, heating on, bowl of water on the radiator to increase humidity, then spray. All bedding on a hot wash.

If the house was empty for a week would that do it?

Is there anything I can put in the washing machine? Some of the dogs bedding can only be done at a lower temperature.

Am I right in thinking its only cat fleas that cause problems?

I remember reading somewhere that freezing kills them (fleas!) so if you have a chest freezer, put dog bedding in a bag and freeze as long as possible

Cat fleas live on dogs too so you need to treat both. November and December are often far worse than the summer for fleas as we turn our heating on and speed up the life cycle.
Leaving the house empty if anything will make things worse for you as they will all hatch on your return in response to vibrations.
Treat all the pets with a prescription product and the house as explained above.

Do you mean if the house was empty would that cause problems on your return? Yes, if it's empty and then you come back, put the heating on and start moving around any dormant fleas in the pupa stage will hatch and look for someone to bite.
If you mean is evacuating for a week going to solve it, then no!