I would suggest that the first and last seedlings are ash trees and the middle one is an elder seedling. All would be 'weeds' in the garden.

I have them all over my garden, pull them out while they are small, when they get bigger the roots go deeper and longer and are a problem to get out.

I agree, ash and elder, I would think there is an established ash tree somewhere near - they seed everywhere. You will know if the other one is elder by crushing the leaves, distinctive aroma.

Hi all thankyou so much for your help.I have now pulled them all up.Shall keep a eye out for any more.Not sure if there is any ash trees nearby .Thankyou again for your help mark

They are really hard to pull out when they get bigger. I have to dig mine out as I miss them every now and then.
Get rid of them is my advice-quick as you can!