Thanks for all those suggestions.
I'll look into the Santa Safari, been to safari many times though, not sure I can face it again.
NT is a great idea, forgot I took DS to Attingham Park nr Shrewsbury when he was 3 and it was very festive, had to queue for ages to actually meet the big fella though! Bit far to go now and I've looked but the other local properties aren't doing anything particularly special.
Wonderland is really good as they make the whole place look festive and you go into a little log cabin with santa on your own so it's very personal and special, can take as many photos as you like.
However I can't praise Black Country museum enough. It's pricey but for a good couple of hours of Christmas magic it is worth every penny...
You're put into a group of about 6-8 children (plus parents etc) and a guide dressed in Victorian dress (and full on Black Country accent!) gets everyone into the festive mood and geared up for the hunt.
Briefly, you go on the tram, into the school house and write a christmas list - be prepared as they don't give you long to do it! - which they take off you to give to an old lady in one of the houses.
At her house she gets each child to stir the christmas pudding mixture whilst making a wish and then the christmas lists get sucked up the chimney!
You go to the bakery and have to find the gingerbread men, go to the blacksmiths and make reindeer shoes and the children get one each to keep and are told to make a wish and leave it out on Christmas eve.
Eventually, you get to Santa's house and after some excitement build up you go into santa's living room and he reads out all the lists and speaks to each child and gives a gift (only down side here is that the room is tiny and crowded and photos are difficult).
Then it's off to the pub for a mince pie and mulled wine or squash.
All the way through you meet local characters who give you clues and you have to look out for signs of santa (his hat on a washing line etc).
All the staff are really good actors, I had a very warm glow at the end of it and DS was so so excited :-)
Once you're in you can go and explore the rest of the museum. We did the Mines and then it was nearly closing time.
You need to book early though as it gets booked up very quickly.
The canal trust tunnel trips which are next door are supposed to be good too but I'm trying to see if our budget will run to that this year.