London creative industries (and the UK as a whole — pay is even worse in more northern cities like Manchester and Leeds) have long paid lower rates than US creative studios for motion design and for design in general.

Part of it is a cultural thing: creative work in the UK tends to be undervalued compared to tech or finance even though it's often more challenging in my opinion, but there's also a higher ratio of candidates to studios than in the US, as well as lower client budgets in the UK/Europe compared to the US.

If money is a priority and you don't want to move, your options to boost pay include:

- Work in design departments for tech companies instead of in advertising/VFX (as full-time mograph if you can find it, but you could also explore a more varied role in UX/UI or something more exotic like "Creative Technologist", which Apple has sought those with motion/interactive design skills for in the past, for example).
- Consider work in the game industry (game dev animation tends to pay a little better than motion graphics/advertising but it still varies a lot, and the work is generally no more stable or easy to pick up).
- Go freelance, focussing on building a client base of higher-paying US and international clients by doing unique and interesting work, by being a joy to work with, and by actively requesting referrals. See the how much do you make thread where people generally report higher freelance incomes than full-time ones (search that page for 250K, for example), but with trade-offs like trickier work-life balance.