If memory serves, it's fuse #1 (or maybe #11, can't remember now) to erase the codes from the ECU - pull the fuse for 30 seconds or so then refit.
The OBD port can only be read by either Volvos reader or the Loki special, a generic OBD-II code reader won't read it as far as i'm aware.
It's great fun finding Kings of Witcham - down a narrow road off the main A142. Long time since i went there but coming from Ely, turn right at Witcham Toll and follow your nose - i think!
The reason i asked if they cleared the codes is because without clearing them, the ECU will still be in Limp Mode. They need clearing so the ECU can relearn the correct fuel trims etc without being in Limp Mode.