Weed ID please

Is that a leaf off the plant or the whole plant? Also how big is it, is it a little bushy plant or a ground sprawling plant? that looks a bit 'woody' at the end, are you talking a soft sappy plant or a shrubby plant?

That's the whole plant. It has rounded fleshy roots which go down quite a long way. It's prostrate, forms a large mat where it can but also pops up near other plants of the same kind, presumably from the same root. The plant in the picture was about 6".

I've now also found it in our garden where it's flat and spreading.

I'm pretty sure that is Field Bindweed, Convolvulus arvensis. The leaves haven't quite developed their typical shape yet. You will have to poison it (glyphosate) - the roots go down to Australia. Covering with black plastic and leaving for several years weakens it but it still comes back!

Thank you Landgirl. Poison it is then. Glad I know what it's called.