Hi. 
Had a fair few issues with my mk3 focus recently. Had it in the garage last week- they have replaced the inlet vents (to hopefully stop the boot leak) and replaced the battery, they also fixed the power to the radio unit which wasn’t turning on at all (bluetooth/usb/voice command still isn’t working but about to order a replacement module as from what i’ve read here that sounds like the issue… fingers crossed). Found a used one for £15. 
The interior lights also stopped working, but have now just sorted this too. 

The parking sensors are the last remaining issue that im stuck on. I get the message ‘Parking aide malfunction service required’. The garage thinks its the module that needs to be replaced (quoted £230 inc labour & VAT to replace). They had none in stock and said it would take a few weeks to get in, so left it for now and thought id try and save some money by having a go myself. I’ve got the unit out, but can only find a replacement with the exact same part number from Germany (ebay). Anyone know what the code actually refers to and whether this would be interchangeable with a slightly different code which does seem more widely available? Part number is; BM5T - 15K866 - BR

Or any other ideas as to what might be worth trying before biting the bullet of ordering a new module (for either the bluetooth and/or parking sensors)?

The boot was filling with water, so I assume the infamous mk3 leak is the likely cause of all of this(?). Seems a reasonable assumption that would cause the issue with the parking aide given that this is located in the boot near the leak, but unsure if/why it would impact the interior light, centre console (BVC, not sync system), and bluetooth. Any ideas? Thanks

You'll ideally need a module with part number BM5T-15K866-B* then R or later as second letter of the suffix

You may get away with an earlier version but first letter of part number suffix must be B

There could be some other suffix combos that work - if Ford have got to R as the engineering level that suggests they’ve done lot of updates, if they got as far as BZ then made further updates they’ll have gone to a new starting letter for the suffix. 
 

Whichever module you get may need software loading too