I am surprised that no one has answered this as there must be someone out there with 2 BeoLines?  I imagine it would work fine, because the situation would be the same as if two close neighbours had BeoLines.  As long as you register to the correct base you should have no problems - that's supposed to be one of the principles of DECT technology.

What 3rd party repeater did you try?  I occasionally see RTX4002s on eBay and wondered if they work. 

Guy wrote:

I occasionally see RTX4002s on eBay and wondered if they work. 

That is the model I tried, just not to keen to buy another  beoline 2 before asking here first.

Any suggestions anyone ?

but you can register a phone to more than one base, and it is quite easy to chose which one to use at any time, so I don't see why this would be a problem.

The Beocom 6000 Mk1 manual also states that you can use 'AUTO SELECT' to chose the other base when the signal to the first is lost - hence implying that the use of 2 BeoLine 2's would work as suggested in the original post.

Thanks Guy. I will get a second Beoline and try "auto select"