In reply to TigerFan:
The best advice to ensure whatever you do is done correctly (ie safely) is to take the stove to a Calor main Dealer since they will be able to sell you the correct hose & regulator & if you're lucky also fit it for you as part of the service.
Local Retailers of Calor such as filling stations etc won't be able to offer help, hence to find your nearest main Dealer Calor's website has a section 'Find a Stockist' which has helpful icons next to each listing to help point you to the right outlet.
The 3.9 propane size is going to be phased out shortly so you're best to obtain a 5kg patio gas cylinder which is the next smallest in the range. Expect to pay circa £70 plus for the initial cylinder hire incl first fill of gas.
Calor is substantially cheaper than Camping Gaz and more widely available in the UK than other brands. However before changing consider the cost of change against the savings - on a camping stove you need to use a lot of gas to recoup the initial outlay! Also consider the size of the cylinder, Camping Gaz is expensive but the cylinder is more easily transported since it about half the size. Finally if you are likely to be using gas abroad then remember Camping Gaz is widely available throughout Europe whilst Calor can only be purchased in the UK.
Post edited at 07:36