The lamp bulbs you need are RS Component Number 655-9722
Lamps are 6v 80mA - piece of cake to fit - simple push-fit.
Cheers
I don't know where you have these specs from, but they are wrong.
In Beomaster 3000 and 4000, the ON, Stereo and discriminator lamps are 14.8V 30mA.
The S-meter illumination lamp is 6V 30mA in either W2 or axial type depending on the brand of S-meter fitted.
Martin