Thanks for the replys
I've been outside in the cold drizzle this morning checking the drain holes again. I'm confident the fronts are okay, but the back ones are still puzzling me.
I poked a very small screwdriver into the rear drain hole and gave it a wiggle. I can't get the screw driver to move inside any further and I can't pull out any dirt. If someone knowledgeable and local to Southampton is able to help me check the holes I would be really grateful.
In the meantime, I have parked the car on a slight slope with the nose pointing downwards.
Many thanks
Matt