I'm posting as this problem is causing me terrible stress and I don't know what to do to now...Sorry it's going to be a bit long as I need to give a bit of background info...
Just over a year ago, my father suddenly decided he either wanted a new wife (who he says would double up as his live-in carer) OR someone to have some intimate time with OR both...so he joined a website that advertises itself as being some sort of a matchmaking service between men (usually Western) and Ukranian women. There's no live webcams. There's no p*rn. Just lots of ladies who appear to want to marry any old bloke as long as they have "love and relationship first" via instant messaging on the site. A little reseach showed this is a scam site, that you can spend £1000s and more and end up with nothing, not even a meeting or a phone conversation. It's clearly (to me) just a glorified chat site, and with no webcam or phone calls, it could be anyone of any gender replying.
So, by April 2017 Dad had blown £3,000 on this site and was utterly obsessed. At this time I hadn't got LPoA, so was legally powerless to stop his spending. I contacted his GP and his social worker, both of whom told me to get LPoA.
I started the process. Dad ramped up his "search". He joined every adult chat site he came across. 99% were scams. He couldn't see it. Every time a site asked him to join, he did. Every time a site asked him for his bank card details, he gave them. Many of them were on rolling subscriptions, and many had "extras" that you had to pay for to be a Gold or Platinum member. At the click of a button, he was paying for those as well. Most of the time he would then forget that site even existed, so he'd paid £50, £70, £100 just to read a few messages and send a few crude ones. I had to phone America, and Europe, etc, to get them to stop the future payments. By now he was spending his small savings pot, transferring money across to his current account so he could pay for even more play.
Eventually I did get LPoA and full control of his bank accounts. In an attempt to steer him towards an ACTUAL relationship, I signed him up for a couple of the legit dating sites, and paid for them (with Dad's knowledge and agreement). He spent an hour or so glancing around each, sent a couple of crude messages, then complained to me that he DIDN'T want those sites, they're a waste of money as "they only have old women on them". My father is 76. He believes that there are hordes of young (18-30 years old) women fighting to have a chance with him.
His social worker said this is all fine, he's a grown man with needs, and he can spend his money on what he likes. True...but here's the stressful bit: he doesn't understand that if he's run out of "play" money why he can't just take it from the rent money, or the money that pays for his carers (he self-funds). His expenditure in the first 6 weeks of this year was £1000. After bills and essentials, he's left with £150 spare cash per month. He doesn't care. We have arguements EVERY DAY now about this. "It's MY money!" he says. His private pension went in on Friday 16th, and I said to him he CANNOT spend more than £150 this month. He agreed. I told him the balance remaining as he spent the money. Today is the 19th - he's spent the lot and was demanding I take money from somewhere so he can talk to his "girlfriends".
One of the big problems is he's bored and lonely. He has no friends wheres he lives, and closest family is over 100 miles away. He has no visitors apart from his 3 brief care visits a day. He doesn't (can't) go out. I can see how this is a substitute for a social life.
So. Saying "NO, BECAUSE" doesn't work, he gets very angry. Ignoring the phone means he fills my ansafone with angry messages and accuses me of not keeping in touch. GP and SW are useless. My brother (IT expert) has suggested he blocks the entire internet until the next payday, but I'm concerned that we'll be taking away his only source of socialising (and one of his only interests - the other being the TV).
So please, any suggestions? How do I deal with this? How do I put a stop to the spending, when "YOU HAVE NO MONEY LEFT" doesn't mean anything to him?
Thanks all 
