I believe the costs would be disproportionate to the benefit of protecting the UK population from what is obviously a minority. There can't be many with HIV, Hepatitis B etc wanting to enter the UK in the first place. Don't forget your list also includes Filipino's trying to come here.
I think "the burden on the taxpayer from health tourism" is actually negligible and may have been quoted in another thread. As to the "considerable risk of spreading the conditions, virus's to the general public", I think is also overstated but hopefully other forum members may be able to provide the figures (Doc Alan?)