I'm not a collector of any sort and especially not of anything that you have to scrub and blanco as the novelty seems to have worn off after a few years of having to do so. But I digress...... I was never aware of there ever being a grey/blue RAF colour sling for the Bren. Rifle, yes, Sterling yes but Sten and Bren, no. But I might be wrong. However, all this absolutely mind blowing stupidity of the Navy having navy blue vehiclesand white webbing etc etc and the RAF having blue/grey vehicles and webbing and the Army having Deep bronze green vehicles and various shades of webbing, depending on which regiment you were with, rightly got the chop by Sir Derek Rayner who was called into look at Admiralty Air Ministry and War Department finances back in the very early 70's.
Can you believe that the various Forces used to pay a premium to acquire commercial vehicles, painted at the factory in a non standard colour like Deep Bronze Green. And then, try to sell them off after 80,000 miles to the public - in a paint scheme that NOBODY wanted! And furthermore, there was not even the remotest possibility that these commercial vehicles, such as cars and mini busses would EVER get within 100 miles of the front line. And the RAF having blue grey webbing and battledress that was camouflaged with absolutely nothing except the sky!!!!! It was ridiculous. But not for long after Rayner got his teeth into it. Thereafter all webbing was issued for land service.
Sorry to go off at a tangent but while I dealt with zillions of various slings, including various shades of khaki, black, dark green and grey/blue, I never saw an RAF grey/blue long Bren sling.
The best stuff I ever had was pattern '44 that we just had to dunk in an old oil drum of warm water and leave to dry. No scrubbing, blanco brass, just as it should be