Thank you all for your replies, a can identify with a lot of it.
Just to add to this I was hoping for a little advice (hand holding really as really worried about DS).
As I mentioned I am now back at work, during school term DS is completely settled and fine with this routine, his clubs etc within the school. The holidays - although he is undoubtedly having so so much fun with his grandparents and cousins who have come to stay up north my partner and I can't help but see him getting more and more anxious.
He has spent time with his grandparents before now, but it has mostly either been with me/the odd few hours here and there. School holidays he is picked up by my mum (and cousins little boy who is staying with her) each day. I see him once I finish work. We have both noticed little signs that we can also remember from when he was first placed with us. Referring to our home as 'your home' either clingy or very rejecting/distant, less eye contact, unsettled when DH comes home (which isn't that unusual for DS). He said this morning (in his anxious voice) "I'm happy because I have a mummy and daddy". Also "who will be looking after me today?" - he has been in the same routine all holidays with my mum.
He also had a nose bleed and had a cold sore, both of which he developed prior to his placement during introduction weeks, FC at the time pointed out this as a sign of his anxiety.
On the surface he is so happy, and we do not doubt he is. But he struggles to express himself, say what he is feeling without 'presuming' what 'we want to hear'. Although he is a cheeky little chap now, he is still quite compliant on the whole. We are concerned he may be subconsciously be picking up on the same feelings as his introduction weeks, being picked up each day, lots of various fun activities, another boy around who is also not with his mum day to day. He has also been bathed around my mums twice which is clearly out of his routine and something we also did in the intro.
Partner and I may well be over thinking this, as you can imagine my mum is ensuring he is ok, and tells me he is fine, but he is always 'fine'. He doesn't shout and scream or outwardly tell us what is wrong at a given time. But we both can just sense this and we were hoping for some honest advice?
Work is becoming a real problem for us, he needs me at home I can't help but feel if I was there, even with the changes of routine in the school holidays we wouldn't be seeming to experience similar 'signs' as we previously did.