Lenton58's favourite bike (from my collection) is my 1955 Raleigh Lenton... it has a 531 frame and fork but is all steel so isn't light but I have taken it out on time trials and put in some respectable times as it is just so smooth and fast.
One would be hard pressed to find one of these as they were not produced in high numbers and nearly 60 years has diminished the number of survivors.
And now for something completely different... my 1966 Moulton F frame which I consider to be a designing marvel and one of my favourite bicycles which again, has had a lot of work to modernize the parts.
These are not hard to find although building one up to this spec would set a person back quite a few bills.