Reusing old blood-test referral forms.

Has anyone had any experience in reusing old referral forms they were issued for blood tests?

I used to be with GenderGP and they'd issue you a £15 blood test referral form that could be used through the NHS to get a blood test completed. I'm not longer with GenderGP and all of the private blood tests I've found range upwards of £140 for a decent panel of results.

There's a date at the top of the form I'd need to change to make it seem recent, though I supposed I could leave it un-changed and just hope they don't notice. None of my personal information has changed that would flag the fact I hadn't requested a new referral either. Just wondering if I could get into any kind of trouble for doing this.

I want to stay on top of my blood work and monitor my levels as closely as possible but with the price of private healthcare here it feels rather impossible for someone in my position.