I get these and assume they are weed trees and pull them up. I'm interested to know what they are too.

Casso if you google images of magnolia leaves they look nothing like this and neither do the leaves on the magnolia in our garden
Take a look at http://www.fotosearch.com/CSP391/k3912755/

The leaves in the image above are different in colour, different in shape, have very marked veining, are slightly serrated, are not glossy... I could go on!

It is a weed tree as Beattie has said and my, and Bulbaholic's, best guess is a prunus - which I told you when you posted the question before.

We do have blackthorns around - I guess that they are seedlings from them.

Ah but they are not a weed you get sloes from them... mind you I think I'd still pull out Beattie

I get these sometimes, they just get puilled up. I also think they are trees.

This is Salix caprea. The slightly coppery young foliage is a common feature as are the two green flaps at the base of each leaf (stipules) seen on the smaller plant at the back. The seed being tiny and with attached fluffy bit can be blown many miles and land in a pot of nice well watered compost. Perfect for it!

We have these in pots of bought in plants quite commonly, mostly I'm guessing from nurseries which obviously have trees in a hedgerow nearby.

Thanks again Fractal! It's nice to put a name to the things you pull out! :-)

Thank you Fractal, I knew my id was only a guess but that it was not a Magnolia :-)

Thank you. I shall plant it in the shrubbery and see what develops.