I'm with eddiecat78 and other GNs here - Sloggi are brilliant! (I've worn them for years.) There are (legitimate) websites which sells Sloggi knickers cheaper than a lot of shops and online shops. It's worth looking around.
I buy M&S and Sloggis. Sloggi are the Mercedes of knickers and if you have had an op would treat yourself to some. They literally feel as if you are not wearing any knickers.
It makes sense. I have never seen seamless knickers, but I also haven't been looking for them. I now buy 5 packs from Amazon when they have a sale on. so far it has worked.