"If I had a Hammer" - Peter, Paul and Mary, I'd help out the OP.

*Get's coat*

To be serious for a moment:

I'd consider why you want a carpet in there, since its likely to suffer from sun damage/colour fade (unless you've got blinds in the conservatory).

Furthermore any carpet insulation might degrade quicker than expected due to the rise & fall of temperatures in a conservatory (usually v cold in winter, v hot in summer).

It really depends upon the location of your conservatory and how you intend to use it.

Personally I think that tiles & an occasional removable rug are the best option, but if you want to use it as a semi permanent room extension then I can understand why you might want carpet.

the best way forward is to get a good company to come take a look at it, they will probably give you all the advice you need just by talking to them when they are there, won't cost you a penny.

They will give you the best advice.

As the others have said, the problem is that the temperature in the summer is very high in a conservatory and insects will love your carpet in there as well as degradation.

In winter the severe cold in there will cause the weave in the carpet to fracture and will eventually thread at a much earlier point.