I checked with RS and they are not planning special offers in the run up to the UK Nationals. However they are planning an autumn discount deal on sails where you can order in the autumn for collection either the following spring or straight away, details all to be confirmed.
I did check with them the current prices of RS Aero sails and they are;
RS Aero 5 Sail: £299.00
RS Aero 7 Sail: £359.00
RS Aero 9 Sail: £388.99