There can’t be many platform games for the Spectrum with two concurrently playable characters. Head over Heels is the only other one I can think of.
Jaime Grilo’s ZXS Spyctrum Mission has you taking the roles of two spys (Allan and Dina) sent to enter the facility where the new ZXS Spyctrum is to be produced and steal the plans for it.
The plans are on 12 floppy discs and there are also 4 prototypes of the machine littered about the facility as well as four keycards to collect. The keycards when inserted into the facilities computer will give out the activation code.
The agents must help each other to reach the various items to be collected and get past the various guards, robots, death rays etc…