100 is a funny multiplier for cars. A car with 95,000 miles is OK, but 105,000 miles is knackered. Over here everything is in KMs and it is 100,000 kms where people think they are going to go wrong, then at 200,000 kms they are a huge risk - but no much difference when they are 300,000 kms - so that's 60,000, 120,000 and 180,000 miles.
Its also funny how, while cars have been getting progressively better engineered over the years and last a lot longer, these '100' milestones haven't changed much in people's minds.
Having said that, £6K or £7K is a lot of moolar for a 100K car. You don't say what spec/year they are - but that's Kiwi prices for a '100K' car - doesn't matter if its miles or KMs - its 100K.
Your comments about rust is also quite amusing. I was chatting to a fellow L Series owner last week in another country which does not put salt on the roads and we were both agast at the pictures on here of the underside of UK cars. Ours both look basically like they did when they left Solihull after being built - whereas the UK cars are all caked in rust. When we work on our cars, the bolts and screws all come off quite easily, whereas on UK cars there is invariably a struggle to combat rust.
So my suggestion to you is to source a Japanese F2. They are RHD and generally cheap, well cared for and rust free. Most of the cars here were not sold new in NZ, they came in at 5 or 6 years old from Japan. You do though need evening classes in Japanese to understand the handbooks and work the radios and GPS systems!