rustle
First things first, if you vote for a strike and you the go sick, rather than strike, you are a fool, in my mind. If you are not prepared to back up your vote, then don't vote or vote against the strike and go to work.
Back to actually being sick. If you have patterned sick around strike days, then no doubt it will be used against you, if you submit a grievance. However, what if you have a compliant GP how isn't busy and is happy to give you the relevant paperwork because you have stress? Then your friend who lives in a different area that has a GP who can't see them, is genuinely sick, but can't get the relevant note.
If your contractual provision gives sick pay and it is refused, then the employer has potentially made an unlawful deduction from wages, as the sickness policy will not have been adhered to.