if you manage to do that to NA Engine somthing is very very wrong with your EFI map tune/ timing way out or your compression is way to high. the chance of doing on that on stock engine running 95 rod is remote
on a high boost turbo car I have seen that many times with a bad tune, but never on a low power Golf 1.8, if you run a digi golf, it will have a knock sensor and unless it has any knock (frequency worked out from bore and stroke of the engine in KHZ) you wont even notice a drop in performance.
My MR2 Turbo is designed to run on 100Ron Jap fuel and with my Blitz ECU its chucks on even more advance and leans out the mix for more power and I chuck in super only, and tesco 99 is the best I have found and have checked this with a timing gun on the rollers - runs way more advance with the Tesco stuff and power than normal Super UL.
The old Mechanical Fuel Injection Golfs Early 8v and 16vs will be more prone to using the correct fuel as they are dumb fuel systems.