Just an update.. I had a blinds specialist company around. They quoted ~€4.5k for the roof blinds for the conservatory. However, I'm still not convinced that these blinds will provide me the insulation I need..they looked wafer-thin. Also, the roof blinds require wires to straddle across the roof so they don't fall down. This will look gruesome. Anyhow, my latest thinking is to use insulating film on the roof. This is kinda like cling film but you can buy the proper stuff from B&Q etc. The roof is double-glazed as is so I'm thinking that this film will make the roof like a poor-man's triple-glazing (or 2.5 glazng). I suspect that the insulation will be as good as the blinds at about 0.5% of the price!