Hi Dave. Most of the conventional/commercially available jacking beams from Draper or Sealey have flat pads which I may be able to secure with velcro staps for safety. However I'm not sure that the trolley jack with the beam in place would fit under. I was thinking I could perhaps drive the car onto scaffold planks to give the extra clearance!!!!!
I have just this afternoon purchased a jacking trolley from ebay with a very low clearance of 80mm. This is the item http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=270686636010&ssPageName=STRK:MEWAX:IT for the princely sum of £35.98!! My intention is to only really use it in conjunction with stands http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=330510400310&ssPageName=STRK:MEWAX:IT for greasing the king pin/race bearing every 1000--1500 miles