My first post and hot for me, I hope it helps some fellow Sony shooters :)
The cheapest price I have ever seen this accessory, currently £229 on Amazon.
Use SUMMER10 - For £10 off to get to £159.
Go through Quidco - QUIDCOFIVE for 5% Discount then 8% cash back takes it under £150.
(Quidco say the cashback only works with the QUIDCOFIVE code)