Where do you belong?

We seem to have acquired a lodger. Ned and I were taking the dogs up to the fields, and in the gateway there she was. She started to come towards us - Piglet was nearly apoplectic - so Ned held the leads and I went to pick her up and take her to what I assumed was her home. But they'd never seen her before, and I know that Ricky and Charlotte in the next house wouldn't have got a kitten because Charlotte's hideously allergic. I obviously couldn't leave her on the road so the people lent me their cat basket to take her away.

She's been scanned at the vet (no chip) and I've asked everyone up and down the road if they know anything about her, and nobody does. She's very sweet and friendly, so not feral. Both the local vet surgeries know we have her, and I've made a nice secure cage (with lid!) from the puppy panels we had stored in the garage. So ....

Do we take her to the RSPCA (not renowned for their helpfulness with strays) or the nearest Cat Rescue? Or (perish the thought) do we keep her and hope she doesn't end up as a tasty snack for one of the dogs? She's very tiny - about 6 or 8 weeks old I reckon (although an expert tells me she must be older than that because her eyes aren't blue any more) - and last time I had a kitten I was 12 years old. I haven't a clue ...

Edit: She's litter trained.