Toilet training regression

[Mallowmarshmallow]

I wonder if anyone has been in a similar situation and can offer advice.

We toilet trained in the summer in a few days, it went far smoother than I could have imagined and all was going well. DS(3) was totally independent in going to the toilet.

Until a couple of months ago. Now we have constant accidents, at least dribbles and if you spot it he still denies he needs the toilet, to full on accidents. This is mainly at home, far less and nursery, pre school and grandparents although occur occasionally.

We have tried numerous responses from ignoring it to being annoyed to offering 'rewards' for successful toilet trips. Occasionally we have glimpses of hope when it gets better for a week or so but then regresses again.

There is a baby in the mix but she is 1 so was around when he toilet trained. (She is also quite hard work, probably far more so now than when he mastered toiletting in the summer...)

Has anyone been here and found a solution that worked for them please?