I'm not familiar with these units. The ones used by MR can be set up to use repeaters. I don't think this is s special feature of the units we use, they're just programmed with the frequencies of the repeater masts.
I don't know what the situation is in the UK with regard to repeaters. I know of 3 or 4 in south Wales but these are set up for and maintained by Mountain Rescue England and Wales. Is there a publically accessible repeater network in the UK?
Also, Even without repeaters, you're grossly underestimating the range of a small, 5watt, handheld VHF radio http://youtu.be/IIMSM-HGfjE