Is it wise to sit TMUA to get an offer from Durham for Computer Science ?

Hello, I was wondering if some Durham CS students or Cs students who have received offers from Durham can comment if it's a necessity to sit the TMUA. On their website they say that they'll reduce your offer if you do well in it. From my point of view that insinuates that they may be more inclined to make offers to people who do it rather than those who don't.
I don't think I'll do bad in the TMUA if I do it. However, for me personally, it would require a lot of time an energy that would take away from my A-levels and overall ucas application.
I'm a contextual offer student if that helps. I also do A-level: maths, further maths and Computer science. Predicted A* maths, A* Computer science and the A* in Further maths is being decided by my teachers (it is definitely an A).
My Gcse's are somewhat mediocre with a majority being grade 7 and 6 due to extenuating circumstances. I hope Durham can see past that.