Hamish: I was of course referring to them feeding on us but I often spot the beggars who are in transit between victims & they're plenty big enough to be seen.
I'm not being pedantic without reason here... But whilst you will see adult and nymph ticks fairly easily, the larvae are small and until they realise how small, many people will miss them and not know they are have ticks on them. Ticks of all ages can, I understand, carry Lyme and therefore it is important that people 'get their eye in' and learn to recognise the small ones.
In terms of the perceived increase in tick numbers, I suspect this is partly due to increased recognition of the problem thanks to the increasing awareness of the risk of Lyme disease. I for one would not have noticed the smaller ticks back when I first started wild camping in Scotland over 30 years ago - I would have a cursory look for things at least a couple of mm across that I could easily see on my skin and been satisfied I was tick free if nothing obvious was spotted.
I suspect that any actual increase will be be due to the net effect of multiple factors including climate change , variations in host species populations, changes in agricultural practices, etc. As much as I'd like to see better conservation management in upland UK, I am not sure we would be able to control tick numbers simply by reducing deer numbers.