Habit/ leaves suggest a type of jasmine.

Many thanks,
My Mum who knows a lot more than me thought it could be a kind of Jasmine, but wasn't 100%.

Hold on a mo ! My head is working better this morning. Solanum Jasminoides. It is a solanum.

this was suggested in the previous post. it does look like a cultivated plant rather than a wild plant.
if you cut the berry in half does it look like a mini tomato? if yes then it is a solanum.

It definitely is a solanum. Did it have mauve or white flowers, 22dreams? I've got a monster in my garden, and have to cut it back drastically each year--in fact twice a year, because it covers the greenhouse and causes too much shade for the tomatoes. You could probably cut yours right down nearly to the base if you wanted too, and it would encourage lots of leafy growth at the base of the plant, rather than just bare stems. Annie