I have a PTV/SRV value from a product specific British Standard test, is this the same as a BS 7976 PTV?

Probably. But not necessarily. Whilst the pendulum will act in the same way on all floor surfaces tested, different methods can involve different sliders or contamination, which may or may not be representative of end use. For most floors you should seek wet PTV’s ≥36 using the Slider 96, for barefoot areas seek wet PTV’s ≥36 using Slider 55 and Slider 96.