Common???? Now now Jerry!!! Non of the above are common, they only happen really when you mod the car and are not common on an unmodded car!! Dont want to scare new or prospective owners!!
OP, o2 Sensor may be where the problem is due to the clank and you have dislodged one of the sensors... Have you got hiflow cats?
Also blinking light dosnt always mean a problem, its a warning, solid light is worse adnd shouldnt be driven...
Where in the UK are you? If may be that someone in your area has an ODB reader and can pull up a code. There is a way to get the engine light to blink at you to tell you what the code is but that is a real pain in the hole to get it too read!
i always thought it was the other way round, light comes on = warning if it turns to flashing = pull the heck over and stop.
i know you know these cars really well so have i had it the wrong way round, its just all the times i hear of a light coming on its been for minimal issues, never really heard of the light flashing at anyone, which is kinda why i thought it was that way round