Radio is not coded, but you might loses the clock and the engine adaptations, leading to a lumpy idle for the first 80-100 miles.
The best place to buy batteries is Vauxhal main dealer, they are rebranded AC Delco premiums. You want the reverse terminal (positive at the front left), a 70aH is ~£96 inc the VAT. My local place does not have this arrangement in stock but it arrived next day.
If you don't get a reverse terminal, this is what happens, the +ve is in the wrong place (rear left) and the +ve cable is just a little too short to be comfortable. The cables are stretched and very hard to fit, and the red cover no longer fits also.
I've now changed this battery.