Current gear: my legs
Achievements: building up aerobic fitness during rugby off-season, basically...getting myself outdoors
Budget: beteen £700-£900
Should be able to get a good bike for that, especially if you use the cycle to work scheme.
The bike I use for commuting now cost me about £600. It's the one below, and is pretty well regarded as an entry level bike. Comes in at £650 so you'd have a bit to spend on other bits and bobs.
http://www.bikeradar.com/gear/category/bikes/road/product/review-giant-scr-15-08-30025
On top of that I'd recommend getting some cleated shoes (ie the ones you clip into the pedals), some mud guards, a cheapo computer and a decent helmet.
For the shoes, I use mountain bike shoes on my commuter as you can walk about in them. You can't really do that in dedicated road shoes.
You can also pick up some good value (ie cheap) shorts in Lidl. Should get you started, and you can spend a bit more if you decide you like it.
As it's summer you might be able to make do without the mudguards for a few months, but they're handy to have as it helps if you want to ride to work or something. You don't want a wet arse/back pack.
It might be worth having a look for your local club as well. Most will do social type rides on the weekend and most are only to happy to have newbies come along. They can be a decent way to meet folks and find out some local routes.
I don't tend to go out with the club much these days, but to start with they're alright.
Wouldn't worry about getting anything more advanced than that until you decide you like it. As with most sports, the kit you can buy is endless if you have the will and the wallet to do so. Those things should get you started though.