Sorry not a very good photo. It has a yellow stripe over its head. Wasp of some sort?

Not clear picture, but the eyes & wings are "fly" like, maybe some sort of hover fly?

If it looks unusual, have a look at Bee Flies.

it looks like one of the Voucella species, a bee/wasp mimic.
poss V. inanis or V. zonaria. Depends on how big they are.

It most resembled V. zonaria in size & colour, Sbg. I’m hoping it will reappear & I can get a better pic. Ty for all your replies. Is the big stripe of yellow on its head just pollen then?

No it is part of its colouring and is a segment of cuticle [skin] between its eyes.

It is one of the largest hoverflies found in the UK.