I'd suggest get it now! It's worth the investment.
Lots of people seem to have the early bird Alpha access. It cost me NZ$103 which is roughly what 49 British Pounds is.
Alpha 2 which will introduce a lot more stuff is due out 24 May, but I take that as UK time, and they're not going to release it at 9 am UK time. It would probably be some time during working hours on that day for the UK.
The game is a lot of fun. Just make sure your PC meets the system requirements. I'd suggest 16GB RAM, a quad core i5 or i7 processor with a clock speed of above 3.0Ghz, and a GTX 970 or AMD R9 390, if you want to play it on 1920x1080 HIGH settings smoothly.
Otherwise you could save money and "wait....." till the full game comes out later....... this year. I know I couldn't do this and hear and watch on YouTube about others having a wooo while they enjoy this game. This game IS fun. And it surprisingly isn't really buggy.