The Ariel was in fact an RH350 and went very well and was extremely reliable. It would easily show 70 mph on the speedo and handled pretty well. The leg shields were alloy and my father had made them and the perspex screen from scratch. (it was originally his bike) The screen may have damaged my street cred but was a lot more comfortable on long wet journey and the daily runs to work at a bank with my suit and tie than was the fly screen on the Hartley Ariel which came later. I don't remember that we commented on the Lambretta screen but the bikes were much more a mode of transport rather than a sporting experience. In retrospect it does look like a mainsail from a four-master though.
I have remembered the tuner's name though - it was Mr Ricardo. That's what we called him when we went round for advice. Looking him up on the net I now realise he was Sir Harry Ricardo. I doubt if we would have dared speak to him had we known!
I will have a look for other pictures but sadly there are none of the Hartley Ariel.