rSAP question (not related to Audi Connect)

I have a Q5 with 3G+ High MMI running K_0942 firmware, NO Audi Connect and NO Sim slots in the head unit.

I also have a Samsung Galaxy S5 handset which supports rSAP and was used with a 'Premium' connection on an RNS510 head unit until recently with great success.

I have used the 'Green' menu to enable the option on the MMI for bluetooth connection to a 'carphone' but, whenever I try to connect it fails to do so and I have to resort to the non-rSAP 'handsfree' mode.

Am I missing something?

I'm really keen to use rSAP as the connection method as I get crap signal on my phone in 'handsfree' mode and really want to use the car's in-built aerial to get better signal strength.

Many thanks in advance.

TD