This is up to 05 model, different for later models but same idea

go to an exhaust kwikfit type centre ask for a free brake and tyre check, they will put it up on a ramp and look for you. you wont be able to look yourself, -but, they should find anything loose etc. tell them the symptoms, and leaning over etc.

then act stupid etc, and drive off!

unless its really dangerous...

that's true. the large chains wont let you under the ramp yourself. The smaller independent ones on the other hand normally don't mind if you ask nicely. Just go in first thing or any other time they're not busy.

Update on cause : checked everything obvious on Sunday with no luck. Got it on a ramp today and established the heat shied "tin foil" relating to the exhaust situated roughly in the centre of the car had been completely bashed about and was rubbing on the centre propshaft. Took a couple of goes to fix as "tin foil" split and had lost all its rigidity. Seems ok now but suspect a new one will be required. Thanks for everyone's input and looking at how this is designed I suspect this is quite a common issue if someone like me thinks his car can aquaplane like a jet ski.  2013 L405 AB 4.4SDV8 Luxor/Ivory, 2007 Vogue TDV8 Epson Green/Sand, 2008 Vogue TDV8 Buckingham Blue/Sand, 2003 Vogue 4.4 LPG Epsom Green/Sage, 1998 Vogue SE 4.6 LPG Epsom Green/Cream

What I said