If you wanted better range then a pair of handheld CB radios would probably be the ultimate solution. 27mhz so considerably lower frequency than marine or PMR, theoretically this improves range. 4 watts transmission power which dwarfs PMR 0.5 watt limit and still no licence required. Having said all that I imagine in real world conditions the performance will only be a bit better than PMR but the price will be considerably higher....starting at around £200 for a pair.

Very impressive- well done

And also the money. Dont forget that most of the work was done by workers paid a pittance. I read somewhere, or saw on tv? that over 1000 lives were lost on building the Manchester Ship Canal. Or isthat a myth?

That's great - thank you so much!