unfortunately there is no easy solution to this nagging problem.. I'm afraid it's a case of stripping the back seat out and only then will you be able to access a square shaped hole in the plate. Twisting a long handled flat bladed screwdriver and hey presto the boot lock releases. Then its a case of linking a wire to the eye hook at the bottom of the unit. while you await a replacement solenoid to arrive from e bay.
Hopefully the lights issue on the number plate should remedy itself when the part is fitted .keep you posted!