I bought my rad from Alternative Autos for about £120, which I though was reasonable for an OEM part.
To replace the rad, you'll need to remove the undertray, wheel arch liners (to provide easy access to the bumper fixings), grille, bumper and slam panel (you'll need to disconnect the bonnet release cable from the catch to completely remove the slam panel).
You'll then need to unscrew the air con rad and surround from the cooling rad. Disconnect the top and bottom hoses, flush the engine through with a hose pipe to remove residual antifreeze and crud. Disconnect the electrical cables from the cooling fans. Lift the entire assembly out
and then laugh at it's condition
It may even fall apart as you lift it out
Unscrew the cooling fan assembly from the rad. It's worth checking the resistance of the cooling fan resistor blocks to ensure they're still OK.
Rebuild in reverse order. Peace of cake
It can be a long job if all the fixings are corroded but perseverance pays off. I did this job about a month ago and soaked all the fixings in penetrating oil beforehand and then rotated the bolts back and forth until they rotated freely before completely removing them. Upon reassembly, I coated all the fixings in copper grease.
Whilst you have the bumper off, it would be worth cleaning the electrical connections on the windscreen/headlight washer pumps and the horns and any other connections you have access to
I don't think I've missed anything but I'm sure someone can kindly fill any gaps
(excuse the pun
I can't advise on replacement of the alternator but I can imagine it will be a PITA job due to the very restricted access. I'm sure someone else can advise though.
Hope this helps.