I don’t think you’ll be disappointed. Hopefully you’ll be having a tasting so you can judge your favourite.
Like @rjsmall I prefer sparkling wines from the 3 Champagne varieties to be black grape dominant, so I prefer the Cavendish blend or the Blanc de Blanc - because there’s £20 difference, I go for the Cavendish most.
M&S’s Marksman is Ridgeview with a M&S label and I was mightily miffed to have missed them on massive discount recently.
@PHarvey - the article says, which is the extent of my knowledge
Pommery was the first Champagne house to produce an English fizz, initially using grapes from Hampshire-based growers.
And at Waitrose 25% off the Nyetimber is indeed cheaper than the Pommery at Majestic, but I’d rather a less expensive one from Camel Valley, Hush Heath or Chapel Down…