Well that is a 1940 pattern uniform, as worn by the Army and RAF (in blue)...
I have seen a pic of a rescued Naval chap in one of these, with his own badges applied.
I've a feeling that as this chap was with Trinity House...and he was at the sharp end of the defence of the realm...He could well have been Home Guard...
He also appears to be wearing his Trinity House cap...but not the accoutrements of a HG chap, ie his webbing and weapon...
There is no reason why he wouldn't have have been in the Home Guard, but that is not a hat usually worn by members of the HG, so he may have been caught between shifts!