Heading over to somewhere like Rutland Water will put you in contact with the kind of thing you're looking for.
If you're commuting, I don't see what the problem is with getting a "racer" and just commuting on it.
A decent racer can be picked up for around £500-600 at the moment, maybe less in the sales. Avoid chain stores and head to a local and trusted retailer
Equally, if your interesting in mountain biking/down-hill at all you might want to buy a decent mountain bike (stiff tailed) and then get hold of some "slick" style tyres for commuting to work - most modern mountain bikes front suspension forks will have a "lock" to provide a stiffer ride for road cycling.
All the best,
Spare Ed