Interesting discussion here.
Over the Bank Holiday weekend, we made our "annual" trip from Berkshire to Swansea along the M4. Now we could do it all in one go, we could do it in 2 goes with a brief toilet break at somewhere like Leigh Delamere, however with a 6 year old in tow, it is nice to break up the journey a little bit, so no MSA stops, but a short detour at Almondsbury to the Garden Centre there. Have a little look around, stretch legs, use facilities and have a nice Brie/Bacon panini and some chips for the little one.
Much more pleasant than whatever junk is being served at Moto and much more reasonably priced.
Coming back, we had lunch at Dyffryn Gardens outside Cardiff and just drove straight back from there.
I try to avoid an MSA except when we absolutely do need to stop for the toilets, which seems to be what most people do - when younger, I recall the tray service restaurants on the M1 and being able to sit and have a cake and some juice in relative peace - using something like Starbucks these days is a whole lot less peaceful.
I don't think I've stepped into a McD of any sort in the last 20 years, so unlikely to do so at an MSA.
Our stops of choice, subject to opening hours are Studley Grange Garden Centre in Swindon and Almondsbury Garden Centre in Bristol. We also found a nice one heading up towards Leicester last year when wiggling across from the M40 to M1, but can't remember what it was called.
I'd much rather pop into somewhere that isn't a big name brand to be honest.