Maybe one of your reasons for this thread might be to try to get a response from the installers you've had recent dealings with? In which case I would wish you luck with that but might still not be confident of a successful outcome.
I don't know the installers you mentioned and haven't heard much about them, so I can't comment on their diagnostics / repair skills or pass on customer stories. What I will say is that it seems not all installers that I hear about (from customers and/or on the grapevine) are apparently any good at diagnostics / repairs, especially on systems they might not be familiar with. On the other thread I did say that 'hiring an ECU' is an unusual thing to do, and other installers that I do respect (Rosko / Tubbs etc) agreed.
I wasn't aware Romano suppliers were in the habit of letting ECU's out for hire (but I can see they might be prepared to do so, some suppliers I have known for a long time might do that for me for free if shove came to push including the nice friendly people at Mint, or I can see some installers might be friendly with other installers that would be prepared to do so). However, most installers should in any case know that most other branded AEB ECU's could be used for the process that one of the installers you visited suggested (doesn't have to have a Romano badge on the ECU). If the installer doesn't have another AEB ECU handy to try on your car, or isn't willing to buy one, then that might suggest they don't fit or do many diagnostics involving AEB systems (and some people would read into the implications - such as possible lack of familiarity with what is still likely the most common 5/6/8 cylinder LPG system ECU in the UK). Some might accuse me of conspiracy theory, but to me by definition 'hiring' implies a charge, which I assume would then be passed onto the customer - But this wouldn't seem a logical way to proceed for an installer that might expect to fit an AEB 5/6/8 cylinder system shortly after looking at your car, while 'hiring' might also imply a time delay before they would be able to continue their diagnostics (some people might read into why a company would want to give customers the impression of a delay, or not answer calls / emails). Most installers will be much more familiar with the concept of buying an ECU and it arriving the next day, and of buying one of the most common ECUs used in the UK rather than hiring.
I recently correctly diagnosed and repaired problems on a Romano 8 cylinder system fitted on a RangeRover, using a different branded AEB2568 ECU (not Romano, same thing just costs less with the different badge) that I happened to have on the shelf (so to be ready to fit for my next 8 cylinder vehicle conversion, nothing suitable to fit it on as yet booked in but even so, I knew I would be using it soon, and I did use it soon, and then I replaced it with another one to keep in stock). I did a bit of a write-up about what I did during diagnostics / repairs on this occasion here: http://www.lpgforum.co.uk/viewtopic.php?f=28&t=13682&start=20
and on this occasion it didn't cost the customer anything for parts.
]Are installers just not interested in fixing systems and would much rather just install new front ends? Or is there something about the way I smell that means these two just don't want to see me again!? Surely there is someone reliable out there who can just get the job done in one visit and won't faff about?
No... Personally, when I first started out with LPG conversions many years ago, I might have been more confident of fitting a new system (obviously with all new components) and getting good results than I would be of repairing an older system but now that I am very familiar at repairing systems (a very wide range of LPG systems) I find it is much easier work diagnosing and repairing LPG systems than installing them from scratch!
I am confident that if you had visited me, your problems would have been correctly diagnosed and repaired (if you wished) during the same visit. Just as I did in the above case (regarding the link), if you agreed I would write up on the forum everything I did during your visit and you would (of course) be free to comment publicly on the forum. If you're interested, my contact details are below. A fair distance from you just over the other side of the pennines along the M62, but you might consider it worth it and I hope to hear. If I can't fix it, your comments on the forum might damage my reputation, but I know it won't come to that!
Full time LPG installer
Servicing / Diagnostics / Repairs to all systems / DIY conversion kits supplied with thorough tech support
2 miles A1, 8 miles M62, http://www.Lpgc.co.uk