After watching the Michael Johnson video on YT I realised that the Holland & Barrett D3 supps I was taking contain magnesium stearate which they say is 'immune compromising'. In fact since I started looking into all this I've binned ALL my H&B supps, what a load of rubbish! I mostly use Lamberts and Nature's Best now.
I'm considering this one healthy.co.uk/products/vita... It's the one recommended in the video.