Oxford - Transferring to another MSc course

Hey everyone,

So I got into the MSc for Software Engineering at Oxford, but I still haven't accepted it. The thing is my first choice would have been the MSc in Advanced Computer Science as I believe I would really enjoy the more in-depth technical courses it offers, but at the time I couldn't finance myself without staying employed so I didn't apply. Thankfully, things have changed for the better and now doing a full-time program is also the option for me.

I wanted to see if the switch is possible and how likely? Would it be better to ask now or accept the offer I have and try to transfer after a year? It's the same department and the college would be the same. I do have a 1st in my Undergraduate studies, but the ACS course is more rigorous than the SE one and there's less space.