No heavy handing here.
Just a very brief note on a busy bit of the site to say if you genuinely have a good reason to decide not to, that is more than fine.
But, all major faiths in the UK support organ donation, there is no evidence to support the fact you get less care if on the register, and it potentially saves your family a huge amount of heart ache if they know what you wanted (even if it's a no).
Have a fab Christmas - and let your family know what you want.