Hi Aztec and welcome to GoY. I can only see one photo looks like a sow thistle and some dandelions - all of which need removing.

Sow thistle is what I see, too. It's edible when younger, but it's likely tough and bitter now. not worth keeping, as MG says. The grass coming up is also likely to be quack grass, or something similar to that annoying weed.

Ive got some seeds from a beautiful blue sow thistle plant that I found but haven't grown them in case they take over.

Blue sow thistle? never heard of those, they sound pretty - just wondering if yours was knapweed by any chance?

I found it in a friend's garden which used to belong to a garden designer for Wakehurst Place a short distance away, so I phoned them and that's what they said it was.

That's Cicerbita macrophylla, Common Blue Sowthistle. It looks a bit like Chicory and is often mistaken for it. It's a fairly common garden escape.

Learn something everyday! Can you post a photo?