Most Ali-tube cable is rated at 90 degs C however FP200 says:-
5. What is the maximum operating temperature of FP200 Gold®?
Minimum operating temperature is – 20°C and the maximum is + 70ºC as laid down in the cable construction standard BS 7629 as required by BS 5839 and BS 5266.
6. Can FP200 Gold® be used at higher temperatures? e.g. 180 - 250ºC.
No, fire resistant cables are tested with a 950ºC flame for a defined period and are unsuitable for re-use after that. Special high temperature cables should be used for applications requiring 200ºC or similar continuous operating conditions.
So reading the specifications Guardian Ali-Tube/LSZH Cable BS8436 is in fact rated higher than FP200 that says:-
Operating temperature: Maximum 90°C, minimum bending -10°C
Since parts of the central heating water goes through metal radiators that you can touch regulation 423.1 table 42.1 gives 80°C as a max so only mineral insulated bare with a temperature rating of 105°C is sure to comply.
I can't see the current rating of FP200 it is not really designed to carry current other than fire alarm one would use other Ali-tube cables.
In real terms any ali-tube cable will transmit heat away from the conductors better than a 624B Twin & Earth LSZH Cable 300/500V BS7211 cable but rating remains the same. With 624Y Twin & Earth PVC Cable BS6004 A05VVH4-U you are limited to conductor temperature of 70°C but with LSZH Cable this rises to 90°C but that is conductor not outside and the conductor will be hotter than the outside.
Again in real terms likely nothing will go wrong, but it does not comply so get him back to change it. Info on cable is here
http://cse-distributors.co.uk/cable/fp200.htm