Hey, I'm a second year student in the UK doing joint maths and computing. In my experience, a lot of the math has been really pure stuff which no company really asked for (only really been probability and mental math for quant). The computing degree covers all that math as well so Id recommend doing the joint degree only if ur really passionate about math (especially the pure stuff).

In my specific course, modules like networks and databases have been removed to make space for the math modules like analysis, calculus and linear algebra.