Road bike buying advice-please help!!!

I currently have a Boardman hybrid comp which I've been using on longer rides with work collegues, we've been increasing the miles each week but I seem to be lagging behind my friends the last two rides. They all have road bikes and seem to be putting less effort into each ride with better results. I've read on forums to not bother with a hybrid and go for a road bike.
NOW THEN...I've made the dessision to sell my hybrid and buy a road bike but as always cost gets in the way! I've been tempted to go for a TRIBAN 3 or 5 £300/£429, or buy another with max £450 budget.
My employer do a cycle to work scheme with HALFORDS but allow maximum £500. I went in to ask about adding cash to get a better bike but they won't allow this as it has to go through the till at £500.
If anyone can help me choose or advise on other options it would be greatly appreciated. :?