Classes for the forthcoming BRCA National Series (
here) are GT2 (1S/10.5) and GT3 (2S 17.5).
If you prefer to run with a 2S pack you already have, then the CRC car will accommodate either 1S or 2S and is probably your best option. None of the Associated cars will take a 2S pack. CRC cars and spares are readily available from AMC in Torquay. AMC will be attending the F1/GT BRCA National series. HTH