Oil at throttle body air inlet vauxhall agila 07 limp home mode?

The car was functioning normally with no obvious issues. On the next journey the engine starts in limp home mode with the engine light on. A mechanic reset the warning system as he believed it was due to debris floating about from a recent fuel and oil system clean. However the next day the same thing has happened, was driving fine, turned engine off, on next restart its stuck in this mode.

Disconnecting the battery for a day did not reset the warning light, its permanent until a tool resets it seems, unless on each start the fault is detected.

I got an error code of 1523 from the computer which from a google relates to throttle sensors. From a quick look I can see some oil present at the air inlet on the throttle body (EGR stuck open?)

There were other error codes but they might of been historic as they don't reappear after the battery was cut.

Any ideas?

More details which may help if you have the patience to read more:

So... a month or so ago a fuel system and oil system clean was performed by a garage as part of a service, I'm not entirely sure what that included.

Recently the car has had a couple of breakdowns the the first time the engine management put the car in 'limp home mode' a mechanic noted the thermostat wasn't opening, so the radiator was not being used and overheating occurred. This was replaced and the car worked again.

A month later the engine light came on again and it was once again in limp home mode. The mechanic assumed it was due to debris/gunk floating around because of the cleaning that had been performed, so cleared the error and the car worked again.

It then failed again (car works for hours/miles, but at next re-start the limp mode is engaged).

I got an error code readout using a 'pedal trick' and several error codes were present (1523,0443,0403,0135,0141,1113) but I didn't know which ones were historic. These apparently relate to O2 sensor heater, throttle sensors, evaporative emissions control system. I wonder if these have been generated due to a wiring fault or if they were historic, I assume over years of use you expect the odd error to collect up.

I disconnected the battery for a day and on reconnect the engine light is still on so some fault is obviously detected at start up or stored in memory, but now the only stored error code is the most recent one 1523 which from a google relates to the throttle sensors.

After a quick look under the bonnet, there is oil at the air inlet of the throttle body, could this be due to the EGR being broken/stuck open?