Finding decent gym leggings is a never ending saga for me so I can relate!! I'm the same - I want a high waist because it is the only thing that will fit my waist and my bum and thighs. I've only ever trusted Lorna Jane but last time I was home one of the girls in the LJ shop mentioned they've changed their fabrics which is a real bummer because my old pairs are definitely best. The one thing I will say is to try different styles of theirs. I agree they all look the same until you try them on - that's when you realise that the cuts vary massively. Look for some of the core stability ones and you should find a winner because they rely less on drawstrings and waist bands and just have a firm panel around the tummy instead. I also have a pair of the Lizette high-waisted tights from Fabletics. Proper high waist but go for a light pattern because as they stretch when you move you can see the white fabric underneath. I'm on the fence about the quality but the pair I have are the comfiest and highest waist tights I've got. Sorry for the essay haha. I just know what a pain it is finding decent gym gear!
I can recommend the Matalan brand of Sportswear, as well as the MyProtein heart shape leggings. Also I hear that Queenie Ke (you can get them on amazon) are pretty good but I have not tried them myself yet.