Ive just bought a new bike and was (still am a complete newbie).
My advice – get a road bike, as previously said Tri specific geometry is only for TT’s and elite cyclists. As your probably getting just one bike you don’t want to have the harsher riding position for your training rides etc.
£1500 will get you s good bike but remember youll have to spend about £300-£400 on additional gear, shoes, pedals, tri bars, pump, multi tool, clothing etc etc.
In the end I went for a Cannondale R800 (only as I loved the look of it), it’s a pretty good bike and has Ultegra/105 components.
Shop around, ask loads of questions, look on websites and find some you like, ive heard good things on the forums about Giant TCR, Specialised Alez and Airnourne. Above all comfort/fitting is the main consideration. I got my bike from
http://www.totalfitness-uk.com/
I cannot speak high enough of their service, they spent 3 hours setting me up with the bike, riding position etc.