if you've got a bit of cash, I would advise doing a size fitting either at cyclefit where you've been looking already or mosquito bikes in islington, £120, best thing I ever did. http://www.mosquito-bikes.co.uk/htdocs/sizing.php
it'll answer most of your sizing questions, can be used for any road bike you intend to build up in the future and means you'll know exactly what frame size would be best for you, which makes it a whole load easier if you decide to go down the ebay route in the future.
they also stock fixie inc http://www.mosquito-bikes.co.uk/htdocs/fixie.php?name=bikes
as well as soma http://www.mosquito-bikes.co.uk/htdocs/soma.php?name=bikes
if you want a couple more alternatives to extend the budget...
if you've got a bit of cash, I would advise doing a size fitting either at cyclefit where you've been looking already or mosquito bikes in islington, £120, best thing I ever did.
http://www.mosquito-bikes.co.uk/htdocs/sizing.php
it'll answer most of your sizing questions, can be used for any road bike you intend to build up in the future and means you'll know exactly what frame size would be best for you, which makes it a whole load easier if you decide to go down the ebay route in the future.
they also stock fixie inc
http://www.mosquito-bikes.co.uk/htdocs/fixie.php?name=bikes
as well as soma
http://www.mosquito-bikes.co.uk/htdocs/soma.php?name=bikes
if you want a couple more alternatives to extend the budget...
happy hunting..