Several issues here and these are purely my own thoughts.
Firstly, assuming criminalisation comes in, the crime will be paying for sex. It can't be enforced retrospectively. It will up to the individual whether they wish to continue purchasing sexual services, but who you have visited and which currently legal sites you have accessed will be irrelevant.
There has been talk of making the accessing of sites such as EI an offence equivalent to viewing child pornography. If that is brought in, I for one will be emigrating as living in a lunatic asylum is not something I find acceptable. Assuming otherwise, accessing the site will not be a criminal offence any more than accessing Swedish escort sites is currently.
Any apprehension for a criminal offence will occur during or after the act of visiting a sex worker.
In Sweden, over 1000 sex workers still make a living in a population not much larger than Ireland. No-one, as far as I'm aware, has been jailed for buying sex in the 15 years since the law was brought in. Plenty of fines though.
The powers that be can access absolutely anything if they want to and being paranoid about IP addresses won't make any difference.
2014 in Northern Ireland:
Number of reported attacks on sex workers 70
Number of sex trafficking cases ZERO