Alde offers it's own antifreeze, a premixed glycol liquid for use down to -37°C. 
 
Alde's ready mixed premium quality glycol for Alde heating systems has a lot of benefits:
 
Provides 5-year protection.
Can be used to top-up existing fluids.
Suitable for all Alde heating systems.
Facilitates circulation and provides a balanced heating system.
Forms a protective coating inside the system to prevent corrosion.
Prevents bacterial growth.
Pre-mixed with deionised water.
Fully intermixable with Alde Premium G13 and G12++.
 
The average UK caravan needs 8-12 litres of fluid for a full flush. 
 
The average UK motorhome needs 10-15 litres. 
 
Alde do not recommend using automotive glycol as this contains incorrect additives and can corrode your system.