I can't tell the size of the leaves from the picture, so it could be a bramble or a rose. By the time it is big enough to see the flowers next year it will be too well established to get rid of easily. I would give it the heave-ho now.
I think it looks more like a rose too farview. I have a self seed growing so far against our front wall, it was impossible to get out so I decided to let it grow to see what happened. Every year it's smothered in white scented blossom and is much admired. No idea where it came from but it is very rampant - very good for pruning when in a foul mood.
I've got one of those, and it's a right pain. It grows between a wall and comes from underneath a big pot, so just have to cut it down whenever, as I can't get to it to dig it up. Gloves definitely needed.
We get lots of them as our house is situated on a plot where people used to come to pick blackberries, so we were told! In fact, we have cultivated some of them along the fence and planted one or two other thornless blackberries too.
Most of them have to be heaved out though, which is not an easy task.
It looks like a bramble or blackberry bush (or the beginnings of one) to me. They grow all round here, but we discourage them from taking over the garden.?
Hi was weeding the garden this afternoon (as you do) and come across another plant/weed I don't remember planting. I'm pretty sure I would'nt have bought it.
I've kept the Foxglove by the way, it's quite pretty now with it's white flowers and the bees love it!