Hi - just started a road trip to get up to Scotland and do the NC500 and my lovely Alphard campervan (2008) 2.4 petrol has started doing intermittent juddering when driving along and occasionally the engine cuts out when parking up and putting into reverse. Any ideas anyone?

That sounds like what I was getting before I cleaned the MAF (made no difference) and then replaced the sensor in the exhaust manifold. If you have an OBD reader (JOBD for these vehicles) then take a look at the codes to see where the issue is.

There are a number of threads covering 'lambda'. 'sensor', 'O2' or 'Oxygen', 'P0171, 'system too lean (bank 1)' and the like. With mine I struggled to get the replacement sensor in as the previous mechanic had stripped the threads on the exhaust manifold - the below thread follows that.