Many thanks for all the comments. The first one had me checking my sums again. I have a L2H2 Boxer van and measured front an rear axel loads with a 100kg bike + 30kg carrier are well within the maximum so I am OK on this. However, on doing some more searching it appears I have been mislead by the information on the PFJones website when it comes to the maximum nose weight:
https://www.pfjones.co.uk/tow-bars/peugeot-tow-bars/peugeot-boxer-towbars.html It states for a van older than 2011 it ranges from 100kg to 150kg depending on the towbar. My Brink tow bar is rated at 140kg. However it turns out the maximum "tow bar weight" as specified by Peugeot for a Boxer van is 100kg and my current understanding is that it is the lower limit that applies. I'm going to follow this up with PFJones. Added to this, there is also the issue that the motorcycle carrier I have puts the weight of the bike around 35cm from the tow bar. I'm still not sure whether this needs to be included in the tow bar weight as this limit seems to be based on trailer use rather than carriers attached to the tow bar. It seems like it should unless there maximum nose weight allows for this. A rough calculation however suggests it could increase the "weight" on the tow bar by another 35%. As such any modern scooter now seems to be out of the question.
Getting a trailer may well end up being the best option but it would be good to keep things compact and transverse trailers don't seem to come cheap. The Hydra Trail is interesting but reviews seem to be rather mixed. I note someone posted that they lost a wheel on a motorway and the response from the company wasn't very helpful.
In terms of a "motorised" option for the motorcycle carrier, it looks like a "vintage" Puch Maxi or a Tomos moped may keep the nose weight below a 100kg. These also have large wheels!!
