Any comment, folks? Reading the page, it strikes me as being very light on evidence.
These debunk most of the nonsense:
Antivax 101: Tactics and Tropes of the Antivaccine Movement
15 Common Anti-Vaccine Arguments and Why They are a Load of Crap
The mercury one is one of the most prevalent pieces of nonsense. The flu vaccine doesn't now contain ethyl mercury (aka thimerosal in the US and thiomersal in the UK) but even if it did, this is not elemental mercury that the site talks about as causing brain damage. The difference between elemental mercury and ethyl mercury is easy to explain by comparing how water contains the highly explosive hydrogen and the highly corrosive oxygen, but when combined in a water molecule, they are not only harmless (except drowning!), they are essential to life.
A good tactic would be to refer them to the NHS website: The flu jab. If they say it's wrong, ask them why they prefer information from their anonymous website as opposed to the trusted NHS one.
There are three fundamental questions for anyone advocating Brexit:
1. What, precisely, are the significant and tangible benefits of leaving the EU?
2. What damage to the UK and its citizens is an acceptable price to pay for those benefits?
3. Which ruling of the ECJ is most persuasive of the need to leave its jurisdiction?