Yes it's great thanks!
I won't lie it's a lot of work, but really enjoyable.
I hadn't done any science since GCSE and then I only achieved C's. Admittedly I sat the GAMSAT a few times, but I was working full-time, had a part-time care job for experience, and volunteered a few hours a week for experience too. After my first application (applied 3 times!) I threw the towel in on my design/marketing job and became a full-time HCA, so I stopped doing my volunteering (as it was at the hospital where I was now a HCA). So that made it a bit easier!
It varies from person to person. I had to study a LOT for it, but it has really helped with the course so far (even though Warwick doesn't require GAMSAT, I'm really glad I sat it because there is a lot of science!). I was studying on average 3-4 hours a day, it was very gruelling. But I found revisiting biology and chemistry incredibly interesting, and thinking about how the science would work in a clinical context really helped spur me on with studying.
Some people manage 1-2hours a day and still do incredibly well. The one good thing we have going for us as arts grads, is that we tend to be able to do the first two sections of the exam with less revision than the scientists. So everything isn't against you!
If money is of little concern to you, I would recommend having a crack at the March sitting of the GAMSAT. This would give you some good prep for the September sitting of the day as a whole, and who knows you might smash it and not need to do the September one. If blowing £250 on an exam for a trial run seems a bit mad (as it did for me) then I would recommend starting revision for the September exam in the New Year (enjoy the Christmas holidays!) doing a minimum of 1-2hours a day.
Hope this helps!