Replacement stereo fitting advice

[Javaman]

I'm looking at a new stereo too.... double din Alphin w235BT.
Currently £120 on Halfrauds....£40 saving over the in-store price.

Any idea on the required parts though to make this work - cage, fascia surrounds etc I will need and where to source?
Halfrauds wanted an extra £75 on top to fit and supply extra parts, plus they insisted it was the store price or no go.........not bad for 20 mins work.....