My MTB is a tank, I have a couple of triathlons coming up, summer's on the way, and I need the right tool for the jobs in hand.

Gonna presume I should do the job properly and not opt for a hybrid. So with that decision made...

Reviews seems to indicate that at £300 this is actually decent and hard to beat in the value for money stakes (but is a gaudy red, not that that matters, except that it does):
http://www.decathlon.co.uk/triban-3-red-road-bike-id_8274036.html

But the range is has just been superseded. The replacement (the 3A for £280) is cheaper, but loses the carbon forks etc. - a step down:
http://www.decathlon.co.uk/triban-3-a-id_8239800.html

But the next one up (the 5A for £400) looks like a real possibility - it retains the carbon forks and adds a Sora triple drivetrain plus a couple of other bits:
http://www.decathlon.co.uk/triban-5-a-id_8239801.html

The 7A for £600 has Tiagra double drivetrain, better wheels, clipless pedals, etc:
http://www.decathlon.co.uk/triban-7-a-id_8239802.html

And at £600 I've kinda hit my budget ceiling at the mo and we're beyond the Halfords Carrera TDF level and well into entry level Giant, Specialized, Trek etc territory. And whilst they might be better known brands and well reviewed, they tend not to be specced as well as the B'Twin 7A or even 5A.

All thoughts and knowledge much appreciated. Ta.