The comfy bra thing again...

I've totally stopped buying bras from M&S recently not particularly because of a problem with the size but the hooks and eyes don't seem as durable. I've got bras which are 20 years old and the only thing wrong with them are the colour has faded or the elastic had gone but there's never been a problem with the hooks and eyes. Now after 2 washes the hooks of my new bras are bent and totally useless.

Miss Mary of Sweden is online but the way you measure up is very clear and I've been happy with the results to date.
I've love to go to Rigby and Peller though they're very expensive

My DD bought some new bras that are the most comfortable ones she's ever had. Yoga bras from Decathlon the sports shop. She knows my difficulty with bras and was recommending them.

I'd never trust M&S to fit a bra properly. Find a specialist lingerie shop and get it done professionally. You can try on all sort there and be given expert advice.

I'm a touch top heavy (34F) and my bras are comfortable and pretty.

A bra shouldn't hurt if it fits properly. If you are a D cup or above, seek out Bravissimo, book an appointment for a fitting. They don't use tape measures but look at the bra on you to see if it fits. They have quite honestly changed my life in the bra department.
If there is no store near you, have a look at the fitting advice on their website. The advice will apply even if you are smaller than a D.