This is very vague, a short book or a long novelette that I read in the 1990s in the UK.
There was a small group of people who find themselves (I can't remember why) materialising on the outskirts of a small English village, by a small hill. They soon learn they're somehow in the mid 1970s.
They make contact with others who've had the same mishap and learn that they can sometimes get back to their own time as random time jumps occur in the same area. However the "jumps" carry great risks as (again I don't remember too much) you will merge with any wildlife that is there at that moment in time, if this happens you can't time jump anymore.
- One person has a mouse head protruding from their arm but it's now part of their body.
- Another has a small bird on (maybe) their chest.
- One really unfortunate individual merged as a swarm of bees was in flight and now has a head full of them.