Giant defy, specialized allez or look for second hand?
I'm basically looking for a good starting point for a beginners road bike.
5ft 6in, normal proportions. Ride 15 or 16in mtb….. Bit of a tenuous qustion but what size road frame?

I've bought myself a road bike to try and was after an allez before I settled on a spesh tricross as wanted something I could take off road/bridleways. Go second hand as you will get a better bike for that money. I'm 5.11 and a 56cm frame is perfect for me.

I'm 5'9" and ride a 54cm Specialized which is suited to someone between 5'6" – 5'9" so I'm between sizes. Looks like you are too so i'd say try both and see what feels better.
I also have a 56cm Bianchi but have a shorter stem on it as the standard 100mm one was a bit to much of a stretch.
Edit; it seems each manufacturer measure their frames differently so be careful with sizing.

2nd hand, get a cannondale R500 from arround 2004/2005 or later for about £300-£350. Then spend the remainder on 2nd hand wheels and a new saddle if you need it.

They aren't the lightest (loses about 0.5lb-1lb to the trek 1000), but most of the excess is in the big bits like wheels/innertubes/tyres and the cranks/BB.

Whats the difference between a cyclocross and a road bike other than tyres? Is the geo that different?

Looks like i can get discount of 20% on bikes via work which means an allez 16 or 24 for as little as £400 or a defy 3.5 for £395. It seems like a good deal so kind of makes the second hand route less attractive. What about old Giant OCRs? Seems like these can be had cheaply.

I'd like to know the same – must be a bit more than just one has bigger tyres?

from a thread t'other day

http://www.merlincycles.co.uk/Bike+Shop/Bikes/Road+Bikes/Felt+Bikes/Felt+F95+Road+Bike_FELT-F95.htm