I lowered the sub frame onto the floor using a trolly jack and when i dragged it out from under the car i found this....

I think it is the holder for the battery and must have fell down when being changed (no i havent checked it see if mines missing yet). Answers on a post card please to Firemans vrs part competition. winner gets a thankyou

p.s its about 6cm by 6cm with a hole in the middle

It is indeed a battery clamp.

Did anyone suggest battery clamp lol

got to admit it gets you guessing when you first see it. not removed the sub frame before so must spent 15 mins looking upwards to see where it came from before i came to same conclusion lol