I acquired a Thermo top C/Z from a BMW3 series E46 (first mistake ) along with a dosing pump a length of fuel line and some exhaust pipe from a guy on eBay - £140 the lot.
Spent a while trying to get it to bench run before I discovered that the BMW units (and Mercedes) have different controller boards that require a can bus signal to start.
Anyway, bought a replacement board from a guy in Lithuania - about £90 delivered, and then diagnosed a duff glow plug as it kept faulting on the ignition stage (second mistake ).
Another £50 for a glow plug and it was still the same - Turned out my test battery was duff coupled with too small wiring for the main supply was causing enough voltage drop for it to fault when the glow plug called for power.
Managed to source a genuine fuel line from pump to heater - eBay again £12 !!!.
Bench test is now all good, fires up good with no smoke and a good clean burn.
Did have some good luck, in the engine bay where the OE heater sits, I found the two plugs for the heater. Tested the power feed and it was live !! - no fuses or relays to fit, and then whilst
changing the exhaust found the plug for the pump just in front of the tank so no real wiring to do except apply a +12v signal to pin one on the heater to start, this I intend to do with a remote relay = eBay again £6 from china - works a treat.
Make note - the supply hose to the heater has to be 2mm bore- otherwise the dosing to the heater is thrown out. Bench testing I used a standard bit of fuel line from tank (lemonade bottle ) to pump and this seemed to work ok.
The other thing to consider is a pick up tube in the main fuel tank. I've got a length of 6mm OD copper pipe and a bulkhead fitting I'm going to use to achieve this.
The word on the street is a Rover 75 unit is OK to use, find a breaker with a complete car to get the heater , pump and exhaust.
If my wiring to the pump checks out ok, I have a spare pump lead that I'm happy to donate to someone's cause if required.