I can't claim the complete credit for this as 'Snoopdroot' (Mike Edwards) gave me pointer in the right direction but I've put the idea into action.
A bit of research on Mike's behalf turned up a matrix that is slightly smaller than the original HC one, it has the connection pipes on the correct side and pointing in roughly the right direction. It's one from an early Landrover Freelander 1.8, pre 01 I think. Mine cost me £15 from a breaker.
Here's the original on the right and Freelander on the left. My original has one pipe slightly modified to fit an alternative valve.
Here's the new matrix showing how the pipes foul on the box, just a slight mod to remove some of the plastic. This the later type box.
The matrix is a 'rattling' fit in the box so I packed it out a bit along the front and the connection end with upholstery foam.
The fan housing could be modified to allow the two pipes to exit roughly through the bottom hole but then alignment with holes in the 'heater plenum shroud' as the manual calls it (heater cover to the rest of us) becomes a problem.
I decided it was better to chop the pipes down a bit and replace with rubber hoses right out through the fan housing's existing holes and out through the shroud to connect straight to the valve or connection to the engine (only later cars have valves).
Sorry, that's the last photo I took before assembly but the rest is straight forward.
you will be flooded with requests for HC rear wheel arch repair panels 
