London theatre ticket sites

[R00tat00tt00t]

I'm planning a short trip to London with DD9 in early January and hoping to go and see a show (probably Matilda or Wicked but open to other recommendations).
Getting a bit lost looking at different ticket sites to try and work out where the best deals are (mid-price tickets) and also looking for NHS discounts if possible.
Are there any specific sites that tend to offer the best prices in advance or are they all much the same? Any tips would be great.

Today Tix app is good if there is a special offer on a show, otherwise it’s cheaper to just buy from the theatre direct.

Usually direct from the theatre is best. I think you’d need to phone up to see if they offer any NHS discount.

TodayTix app is good for when there are special offers on.

Matilda also do a lottery which I’ve won twice for premium tickets at £25 each.

Thank you! I'll take a look at that app and also the theatres own website/ticket office.
Could you tell me more about the lottery please? Where would I find it?