I doubt that you will find a Toyota specialist in London, particularly for that model since very few were brought into the country.
You say you have a leak from the Intercooler or is it into the intercooler (I assume it has an after market turbo and intercooler)?
Oil build up in an intercooler is quite common. On the pipework between the air filter and the turbo you should find a crankcase breather that comes from the top of the engine/rocker cover. This can suck up oily air that then ends up depositing the oil throughout the air intake pipes and intercooler.
It would be more worrying if you had oil in the intercooler and also a smokey/oily exhaust which is a sure sign of impending turbo bearing failure - as the bearing wears it starts to wobble causing oil to leak out on both sides (I've never come across it leaking out of one side only, but it could happen).
I guess one way to check is remove the intake pipework on either side of the turbo and compare the quantities of oil. If there is a lot more downstream from the turbo, then it might well be leaking out of just one side.
I hope that helps. I'm not London based, but you are welcome to call me on 07971 540 362 to chat through some options.
Also, if you join the Euro LC Owners mailing list (see my sig) there are plenty on there willing to provide further advice on this and other LC related issues. You might be able to pursuade another LC owner locally to you to come around and provide a second opinion, which always helps.
Euro Landcruiser Owners Club
- Specialising in Land Cruiser preparation and servicing.