Bumpkin, if you can get the supplier details it would be a big help

I'll open up the radio and check if it has the same metal chassis as the earlier model, I suspect it will.
Have sent him a text, will let you know.
Bobbin-Man said:
If it is similar and I can fit a socket, what specification do I need to look for to get both an antenna and a replacement aerial for use as a hand-held? I'm seeing all sorts of information such as UHF/VHF/Dual band/SMA ... it's all foreign to me! I assume that the aerial swap will not affect the ability for the PMR to be Autocom powered?
I've just looked it up and the TK-3310 is a CB band radio but, it appears, for the Australian market, not PMR446. It's possible that you're talking about the TK3301 which is a PMR model and supersedes the ever popular TK3201. Your mention of 0.5W power output suggests that yours is a TK3301.
So for the time being I'm going to assume that you did mean the TK3301...
The Bikers Oracle kit will work fine, it's a PMR tuned, i.e. it's the correct length for the frequency (445MHz + 20MHz range). I have one and get decent real world range of 2-5km, obviously depending on terrain between my and a similarly equipped bike. Admittedly this is using Puxing PX888 radios at 4 watts, though the higher power doesn't increase the range by anywhere are much as you might think. The inverse square law dictates that, theoretically, you'll need four times the power to double the range and even then in the real world there are other factors that reduce this further still.
The Autocom will still power the radio OK. It's the higher output radios, i.e. the 4 and 5 watt business radios, that draw too much current for the Autocom to cope with, or so they say. The BO antenna won't make the 0.5 watt radio you have draw any more that it was before. The advantage it will give is making the antenna vertical, removing it from under the seat and putting it in a better position, you should be impressed with the improvement. I've now done away with the BO number plate mounting plate and have the antenna higher up near the grab rail of my VFR. Someone I was touring with last year had a set-up like this and it worked well. The BO number plate mount works fine but I thought I'd try for just a little more... I also melted an antenna in the hot exhaust gasses with the BO plate...
If you can convert the radio as suggested then you will probably wind up with a
male SMA connector. You will need to buy an SMA to BNC converter to use the BO antenna (they sell one, it's an option in the kit). For a hand-held antenna you will need a PMR tuned UHF (400-470 MHz) antenna with a SMA-F (female) connector (assuming that your conversion leaves the radio with an correspond SMA-M, i.e. male, connector). There are plenty on eBay, go for the regular length, rather than the stubby ones, IMHO.
If you're riding with others with radios and standard antennas horizontal under their seats you're not going to improve the comms situation much, they should be able to hear you a bit better but you wont hear them any further away than you already do. The real gains are when both parties have the BO kit installed.
VHF = Very High Frequency
UHF = Ultra High Frequency (where the PMR bands are)
Dual Band = Equipment that will cover both of the above frequency ranges (there are radios as well as antennas). The TK3301 is UHF, not dual band.
SMA and BNC = These are antenna connectors; SMA screws together, BNC has a bayonet type fastening.
HTH