After posting this http://thegreynomads.activeboard.com/t60459418/disaterous-first-trip-horrible-noise-when-towing/ I have finally got the mechanic out to check things out and do a full service on the wheels.  This was a fiasco in itself as I had booked the mechanic to home visit, at 9:30am, and had to take some time off work.  Come 10:00 I phoned up the caravan  place asking 'where is he'  to be told I had been booked in for a service but me bringing the van to them.  After sorting this out - the lady did remember me luckily I asked when the mechanic could get here and was told she would contact him and get back to me, at which time I found she also had my phone number down wrong as well.

Long story short I was told he needed to return to the workshop after finishing his current job and pick up the needed parts, so would be at my place around 11:00.  At 11:50 the mechanic arrived!  After doing the servicing (which I was watching) he reckoned that the original (sales) yard had set the brakes too tight, and they had heated up to cause the noise.  All up the service was around 1 1/2 hours

Due to the late hour of finishing I was unable to test tow the van as I was already a further 2 hours later for work than I had originally organised.