Different caravans have different chassis. If your has a Alko chassis it should fit but best to check and ring them and ask. They did tell me though that they thought their carrier would not fit my 1991 Alko chassised caravan but as it had the relevant fitting holes I bought one and it fitted fine. I did ring them back to let them know for future reference.
The Alko wheel carrier is telescopic and as mentioned there are four different sizes to ensure the correct fit for your van chassis. Check on there website here, as there's a requirement to check a specific measurement/width of the chassis to get the right carrier.
There's a lot of criticism of the carrier as many have found them to be jammes/siezed shut when they've come to need them, but with proper maintenance I find mine works well. I withdraw the rack several times during the year and apply copper grease or similar to the frame and sliding tubing and something you should consider as and when you get one.
You might also be interested in this firm here who advertise in the caravan mags their own version of wheel carrier that they claim is good for all known chassis. Current price in CC mag is £38.50 + £11.50 carriage, a fair bit cheaper than the Alko. Scroll down the right of the page to find "Caravan Spare Wheel Carriers".