On which uk auction site can I buy bulk products and then sell on e bay for profit ?

Unfortunately because the UK is such a small place I think the golden age as diminished somewhat in this area. Ebay its self has job lot and pallet sales, but they tend to be faulty goods or damaged needing knowledge and time to make saleable. Best bet is of course bankruptcy sales try those!

Have a big bank balance

I think you need to find wholesalers.

You'd probably have more luck on something like MSE than on here tbh