Welcome to the forum.
Every day is a school day - never heard of a Virage, I'm guessing it was an early successor to the Futura, possibly built early 90s.
Check the build plate on the transom as that will give you the year of manufacture. Material will be Strongan Duotex - basically Zodiac's own PVC material. I see Chas Newens still sell speed tubes for it.
In terms of sizes - floors should be interchangeable with Grand Tourism and Futura at MKIIC size, with the bow board, thrust board having opening for the keel valve, then three interlocking floor sections. The aluminium floors (HD) are nigh impossible to source separately and if you can find them, they will command your kidney as payment. They are held in place with two stringers either side.
Post up some pictures - would be interested to see it.