may need to swap the live and switched live wires round on the new radio harness, often they have bullet connectors for this. plus may have to add a switched live as most MK2 dont have them as standard
My 89 CE1 16v didn't have a Live After Ignition, I wired it to the Heater (Black/Red) like everyone else has done.
I would recommend you go to the glovebox light power instead, theres a 2 pin spade near the radio you could use. even the poverty spec have this plug, just missing the extra bit that goes to the light. to avoid damaging existing harness you could even make a short piggy back loom to go between this plug and glovebox bit or for CE1 you have 4 ignition live spades on the fusebox G spade 1,2,3 or 5 easy peasy