I’m very sensitive to noise coming though the party wall. My 1910 semi is especially bad but my friends 1970’s terrace is like an anechoic chamber inside so would be prefect for me.
If I’m looking to buy a house how can i determine how good the sound insulation is likely to be? Sadly I can’t afford a detached house!

Dunno, but if it’s a deal breaker then when looking at a place take a friend and ask the seller if they mind introducing you to the neighbours and have one of you go next-door and make some noise?

By way of bonus you’ll meet the neighbours and see if the seller has been getting on well with them!

We are end of terrace and have tweaked the layout so all of the living rooms are not attached to the neighbour, just bathrooms, corridors, laundry room, spare bedroom etc. It was mostly like that so wasn’t too tricky a change. The neighbour is quiet now but that isn’t a given. It is also possible to add sound insulation to the wall if you are happy to lose a couple of inches of interior space

I’m thinking of doing that to my current house however two of the upstairs doors have their lining fixed directly to the party wall – I can afford to loose six inches off the room width but I can’t have doors that are six inches narrower! (because of the head of the stairs the doors can’t be moved over).
My house is long and thin – its only effectively one room width wide at ground floor so rearranging things also isn’t an option..