Yo Squiffy
I've never tried Autocom, but appreciate that they are regarded as 'the best', but are also damn expenisve if you want 2 x radios plus all the other kit. The Intaride complete system is a lot cheaper, and does the job perfectly (for me anyway!)
I have the Series 99 radios, the 80 wasn't available when I bought mine a couple of years ago. From what I know, the 80 'can' transmit at 2 watts (which, without a licence, is illegal I believe! but that's the owners call

) whereas the 99 is only a legal .5 watt, so the tx distance on this one isn't great. I use mine for training and so the guy I'm talking to is generally very close in front of me, so I wouldn't want to state exactly how far you will get with the 99, but I'd guess it was less than a mile, and then only when there is nothing else in the way (hills etc). As far as I know the only differences between the 2 are the extra power of the 80, plus it's waterproof.
So I'd suggest the 99 is all you need, going by what you said. Must admit I'd like to try the 80 out some time, just to see how much further I could get, even though I don't actually need it
HTH
fester