It could be a type of Hawksbeard or Hawkweed? You will need to see what the leaves look like as the flowers are similar. If you like the plant and it's not too invasive then leave it be. It will be a good source of pollen for early flying insects and any flowers that appear in woodland shade must be encouraged. Early insects will need a reliable source of food to keep them going until we need them to pollinate all the fruit trees etc.

Could possibly be coltsfoot, but will ahve a look in my books :-)

This may help www.eatweeds.co.uk/learn-about-coltsfoot says it is a member of the daisy family and is one of the first to flower around the same time as crocus

I think it could be coltsfoot, but growing much earlier than ours. Coltsfoot or Hawkweed, I suspect that it is likely to be very invasive as it broadcasts it's seeds.

Looks like Colts foot from here.

Looks like coltsfoot to me... invasive.

and t me too. I loved to pick these as a little girl as they were one of the earliest wild flowers to flower. a true sign spring had sprung.

Thanks all who replied. It looks as though this is not a particularly welcome visitor - I will have to show it the door!