Looks like Eucryphia to me. a nice buy if it is.

found this from the RHS,
may be yours or closely related

https://www.rhs.org.uk/Plants/94255/Eucryphia-x-nymansensis/Details

It looks remarkably like Carpenteria californica to me, though the flowers are usually fragrant to a lesser or greater degree. It's not bone hardy though, same hardiness rating as most Hebes, H4 rhs rating, but is evergreen. Its not a common plant in gardens or garden centres either - often commonly known as bush or tree anemone

https://www.crocus.co.uk/plants/_/carpenteria-californica/classid.691/

Thanks Seaburn, it certainly looks like it, or very closely related. Says it eventually grows 20-50 feet, so that will be interesting, but perhaps I shall be long gone before then. Must look stunning as a large tree covered in those flowers.
One of the local nurseries used to, not sure about now, have a section where they bunged everything that was either weed infested, un-labelled, mis-shapen or just needed to be got rid of and sold them off at two for £1. Loads of things came home with me over the years, including Catalpa, Red Robin, Ceanothus, Broom, Strawberry Trees, Several different Cornus and loads more, just to plant on the field as hedges and windbreaks. This one perhaps a bit more special!

Got all excited about a 50ft tree and liked the idea Seaburn and answered before the next suggestion, but I think Bamboo might have it here. I got OH to have a whiff of the flowers and he said they have a faint scent, sense of smell in our family is not good, so asked him!
A two metre bush would be a better fit where it is on the field! Shame it's on the field and not in my garden.
A different site than the one you gave Bamboo shows the dark stems and the round ball shaped buds, so I think that's it.
Thank you both for sorting it out, I shall probably put some netting round it now to prevent the chickens half digging it up all the time, poor thing. And a label!

You're lucky to have it - it was one of my desired shrubs years back, but I never was able to get hold of one. Now I've only got a balcony, its not an option, but I think they're a lovely plant.

No worries, as I said it was just what it looked like. Glad it is going to be a better sized shrub for you.

I agree with Bamboo, Carpenteria californica was my first thought. Quite expensive shrub though. A neighbour has one in his garden but I don't think he knows what it is.

It's quite an impressive looking little shrub at the moment Bamboo and I am so pleased that I know the name of it now. Perhaps you could enlighten your neighbour Jimmytheone, or is he the type that doesn't want help?