Patio heater cable requirements

I have just had delivery of a Futura Deluxe Wall Mounted Electric Infrared Outdoor Garden Patio Heater 2000W, but the cable is too short. I need to replace with a longer cable but im not sure what is acceptable and what is not. 

Current cable is h05rn-f 3g 1.0 mm2. Does it need to be exactly the same or would be something similar be ok? struggling to find something online between 5-10 meters. anyone point me in the right direction of where i can get something suitable. 

Appreciate help with this. 

larger distances will require a larger cable. best option would be to get an electrician to install a fused spur / DP switch adjacent to the heater and it can be wired direct into that

Black H07RN-F cable would be suitable and would be the preferred cable for this application, however it is thicker than H05RN-F and may not fit through the existing cable entries in the product, but you must not reduce the conductor size.

H05RN-F cable is the same type as "pond flex" 3183P this is available at 1.5mm² (which might be a good choice but may be too thick for installation)  from Screwfix in 10m rolls.  1.0mm² seems to be an unpopular choice and generally unavailable.

H05RR-F (tough rubber sheathed cable) and 3183Y (black PVC flex) might be OK so long as the cable is not in permanent damp.