This question gets asked on a daily bases we are not allowed to give advice on selling lamps and how to make them legal according to the LIA (Lighting Industry Association)
However we have found a nice link online with a decent amount of information that should hopefully make sense and give you a basic idea on how to make your lamp safe and legal to sell.
A quick disclaimer:
The following website is no way associated with Lampspares.co.uk and the information on that page may change without notice.
We cannot say if the information there is 100% correct so please do further research if needed.
Contact the LIA here for further information if need be.