Afternoon all, I'm new to the site. 

I did see some guides to how to pick your new bike but I can no longer find them, can someone point me in the right direction, thanks?

Also whilst here I may as well ask for your recommendations. Currently I commute to work by bike (a Viking Urband Legend hybrid). I've started doing triathlons and I'm thinking about a new bike that I could use for both commuting and triathlons. Something like a Giant GoAnywhere but cheaper would be great. 

My budget is £500 and I did consider the B'Twin Triban 500, although I think I'd like thicker tyres for the dirt paths and cobbled streets I go on. I'd also consider second hand but I've no idea what's a good prices to pay.