To those who replied to me in the part 1 thread:
The Sena SRL2 intercom I use is designed for my helmet and mounts inside, so there is nothing jutting out or clipped onto the rim of the helmet (like earlier designs I had). I used in-ear and clip on intercoms whilst I was learning to ride and found them intensely uncomforable. With the SRL speakers and mic installed there isn’t really any more space inside for additional speakers or mics, and I tend to wear earplugs to reduce noise (which the Sena intercom is designed for and can get very loud to overcome ear plugs!).
The Kenwood isn’t waterproof (IP67 or similar). In my experience if you are touring on a motorbike and hit bad weather, the rain/water can and will get everywhere eventually! The Motorola looks nice, but I’m not prepared to sell my soul for one! The prices I found were about £1k.
Whilst I’ve not operated 2m on the go on the bike before, I use the intercom regularly with other people I ride with, or take phone calls. Operating on 2m shouldn’t but much different, if I can find a suitable setup, where I have adequate controls (PTT on the handle bar that toggles rather than press and hold, easy and accessible ways to QSY from 145.500 for example). Just like using the intercom, it’s most useful on the highway/motorway on the longer drives to talk to the people around me, but with even more range and a wider audience.
I use a tank bag whilst touring and may use this to put the radio in. My bike has a 5amp accessory socket near the yoke which I already use to keep a powerbank charged during the days riding, but could also power a small radio or handheld, but might need some filtering as motorbike alternators can be pretty noisy.
I’ve been doing some reading today and (thanks to @EA4WT 
) I’ve ordered an Ailunce HA2 from Amazon for a paltry £84, which gets some really good reviews about its’ hardware (good output and low spurious emmissions) and it is IP67 rated too. The battery looks huge (2800mAh rated for 77hrs standby) and charges from USB C too (so no extra wall warts needed in the paniers).
I’ve also ordered a RAM X-grip to see if it’ll hold the radio on the bike securely. RAM are pretty high-quality products, but I’ll see if the radio seems secure. They are designed to grip phones upto 0.875" (22mm) deep but the HA2 is 1.5". I might be able to 3D print some deeper grips or use some sort of rubber band to help secure it. Either way I’ll probably use it for other vehicles, or return it if it really isn’t up to my needs.
Otherwise, I might see what I can do with the belt clip mount on the radio itself or simply relegate it to a tank bag, similar to what Armin did and forego QSYing on the move.
I have to pop back to ML&S over the weekend to return something and will see what aerial mounts and aerial’s might work for the bike. I guess I’ll be limited to coil loaded antenna or a center fed antenna as I doubt the bike will give much of a ground plane. It may not be worth doing anything and just using the rubber duck supplied with the HA2 Getting a bit off-topic, but any suggestions on motorbike antenna’s? I guess it’s even more niche!
Thanks for the info chaps!
73’s
Dave.