Do you pay for lounge access if not included with your ticket?

I'm taking my 2nd non-*A flight (other than short discount) on THursday with Qatar Airways from LHR-DOH. The 1st trip was in J, so I got lounge access included. I'm trying to decide whether or not it is worth paying for lounge access.

I looked at Priority pass, but I really do travel most of the time with *A (lounge access included) or in J (the other legs of this trip - lounge access included). The price just seems to0 high for my needs.

I am thinking about paying for the Servisair lounge in T3 at LHR. I've been in the MAN lounge (as a *A) and... well.. definitely not worth the 18 quid that they want for LHR.

If I do pay for it, what is the best way to pay? The www.executivelounges.com website is quoting me 17.50. What if I show up at the door to pay?

Things that I look for in a lounge include internet access, comfort, food and drink.

Thanks,

Dr. PITUK