I'm assuming Spain pulls an Italy, in that she waits until the Summer of 1940 to join after France falls. In such a case, the British Army is far too lacking in forces to conduct such an operation and what they do have is needed to safe guard against the threat of Sea Lion. By the time the British have the shipping and forces to do such is probably early 1941, in which case the Spanish will have been able to heavily fortify the islands; the Brits can still definitely take it, but the resource expenditure is going to mean they have to make concessions somewhere else. Say, for example, they don't reinforce the Greeks come Spring when the Germans intervene there. In that case, it's entirely possible the knock on effects see Barbarossa collapse the Soviets.