See this item, the Atlant kit: http://www.ikea.com/gb/en/catalog/products/20215523/
You need it for the little plastic rectangle, seal and hose which connects the overflow to the rest. Everything else is shit and should be thrown away. The trap is a piss-poor design and leaks like a sieve, and it is completely incompatible with standard UK waste pipes. Go to a plumbers merchant and buy a normal basket strainer that connects to a standard bottle trap or u bend, and a single or double appliance attachment as needed.
See this item, the Atlant kit:
http://www.ikea.com/gb/en/catalog/products/20215523/
You need it for the little plastic rectangle, seal and hose which connects the overflow to the rest. Everything else is shit and should be thrown away. The trap is a piss-poor design and leaks like a sieve, and it is completely incompatible with standard UK waste pipes. Go to a plumbers merchant and buy a normal basket strainer that connects to a standard bottle trap or u bend, and a single or double appliance attachment as needed.