Don't worry Piers, it'll be fixable one way or t'other! ;)
No advisories regarding this issue on last MoT (although other items picked up last time, not mentioned this time!!) same tester as well!
The ironies are thricefold:
1) Winter is coming, which is why I got an RX in the first place to get me into work in rural Dorset - an RX with no MoT means rally crossing to work in my much older and tenfold less rusty MR2!
2) I'd finally finished refurbing the last 2 alloys which I had tyres in the garage ready to go on (still got it done today tho!)
3) Original exhaust and cat 13 years on and zero emissions problems! (Although rear exhaust hanger fell off last year due to rust and was 'fixed' with a heavy duty stainless steel style 'cable tie' to original mounting point!)
With air suspension spares tucked away in the garage, clean alloys, clean body work & interior and the knowledge the engine is still sweet as a nut with zero electronic issues (possible conversion to LPG as a new year project on the cards), there's still loads of life in the old girl yet! Bearing in mind I paid £4K for this car 2 years ago and have covered 20k miles, I think I can stretch to get this sorted and still have miles and miles of luxury cheap reliable motoring to come...
Compared to X5's, tourag's, cayenne's and ML Mercs etc, where I'd have no doubt oil leaks, failing gearboxes, dodgy electrics/electronics, higher insurance etc etc etc, the RX truly has not disappointed. Rust is somewhat inevitable in the U.K. and I can't blame the car for the environment taking it's toll on it after 13 years.
As other members have suggested it is worth undersealing the car to avoid this situation, no doubt I'll be doing that too if I end up sorting this out myself.