Hi, and welcome. I'm new to the sport also, so am in a similar position as yourself.
A few things I have learnt so far may be of interest to you.
With an 800 quid budget for a bike, you should be able to pick up a decent one, especially this time of the year. But, IMHO, it is more important to get a bike that fits you. Also, as said, budget for shoes/cleats/pedals. With that budget I'd be partial to trying to get a decent turbo trainer for setting up your bike indoors. Oh, and a garmin cadence sensor, and an ant + USB stick, and a subscription to trainerroad.com. The list goes on and on, as you will find out.
Ref your wetsuit, I wouldn't worry too much about it until your closer to the day, and then go into a shop to get fitted for one. How's your swimming?, I've only been swimming the past 2months and am only upto 2 lengths without having to stop for breath.
I agree what dust boy said about bike, bike and more bike. The run seems to be just to see if you can hang on in there lol
Good luck with it, and keep posting on your progression. I'm sure someone who knows a lot more about all this than me will come along soon and pipe up. All the best.