Hi Adam.....welcome to the Club
I would think that summer tyres are fine for the UK unless you live in remote areas with heavy rainfall.
All season tyres are okay to use but will wear out quicker and cost a lot more usually
Hi Trevor......welcome to the Club
You could take a feed from the ignition feed to the new stereo head unit.
Alternatively, Halfords sell aftermarket radio adapter leads to plug straight in and this would not affect any other parts such as the clock
Hi Luke.....welcome to the Club
I would say you are correct that it is the antenna and as far as I am aware it would not need coding to the vehicle as it does not generate or hold the immobilise code (the ECU would have that information) it simply amplifies the signal from the immobiliser chip in the key fob
Hi Stephen.....welcome to the Club
It could be a central electrical fault, anything from a battery connection to the fusebox and associated fuses.
Careful examination of all connections and wiring leading from the battery to the fusebox may unearth the fault.