beeping noise driving me mad!

Right, I've just spent a small fortune getting my TD5 Disco 2 sorted. Fuel pump, brakes lines, diff's stripped and re-sealed, some pinion steering thingy, transfer box oil leak sorted but I still have a really annoying beeping but no warning light. It starts after around a minute of driving and seems to last for a minute too then it stops. The car doesn't drive any differently before or after the beeping. I have been told that the ACE has been disconnected (probably because of a fault) and wondered if it could be this? Would the car beep to say it's not connected/working? Could it be a seat belt sensor? It really does irritate me and when people get in the car and it's beeping they take the **** saying "landrover broken again?" and "should have bought a shogun" phish!!!

Are all the warning lights for the existing systems working on ignition self test?, maybe the previous owner blanked only the warning light and you get the audible fault warning without seing the lamp too

I had this my tc was switched off and also hdc. check they come on when you turn the ignition on

I've also heard people tape over the light behind the dash so the light comes on and you cant see it. I took the dash clocks out to check