2011 TDV8 50k miles. Just recently I've noticed that on hard acceleration after long periods of slow driving or sitting in traffic, there is a fair bit of grey exhaust smoke. Will this be the particulate filter clearing itself or something more serious?

I reckon it's your DPF  Present :2008 TDV8 HSE
Gone Audi A5 2.7TDI
Gone Discovery 3 HSE
Gone Mercedes CLK
Gone Range Rover 2.5 DSE

if it was the DPF would the warning light not come on first?

last year my previous 3.6Tdv8 did the same thing on hard acceleration and forum members correctly diagnosed that the issue as a split air hose. 2011 4.4 TdV8 Nara Bronze

+1 for a split air hose - worth getting it checked as it's a very east fix  2007 Zermatt Silver TDV8 Vogue SE - now sold but was a great car!