Also worth mentioning, replacing the ecu used may be folly. I tried two “working” ones on eBay, both failed quickly leaving me high and dry. Bought a new part, flawless! Cost wasn’t cheap, but a couple of hundred was well worthwhile to know it wasn’t going to leave me needing a tow
Edited to say, the beep can be resolved short term, take the handbrake off and pull those fuses..... no handbrake, but also no beep!