FYI I'm a student.
Sorry, what's the issue? YABVU with this passive aggressive mentality. You've apparently raised an independent child whose life doesn't revolve around you (and at 21, good) and now you're complaining. Ok, his communication skills could be a lot better, but telling him you won't give him money that he expects, this close to january rent, is a really bad idea if you want him to talk to you more.
There seem to be 2 issues -
1, he doesn't talk to you
2, you think you're giving him too much money (because if you didn't, you wouldn't have mentioned it)
If you want to only give him money if he talks to you at certain frequencies, then you'll get your weekly chats or whatever whilst you're giving him money, but as soon as you stop, you're probably never going to talk to him again. Not recommended....
If you want a decent relationship with him now AND when you're not giving him money, then resolve 2, and hopefully 1 will come when he realises his parents are important (that's not something you can speed up. You can definitely slow it down though, perhaps by cutting off rent money that you and he had agreed he'd get with no warning at all).
To resolve 2:
His essential outgoings are: costs to get to/from uni, and rent.
His income is a student loan.
Do the maths, and I (as a student) would recommend that you give him (at a bare minimum) however much money is required so that after all essential outgoings he has £60/ week spending money. If you can give him that without any strings attached, then that's great. If you can give him more, even better, but I wouldn't recommend giving him more than £80/week regardless of how rich you are (I get £75/week from my parents and that's plenty (i don't drink)- realistically most students will piss the extra against a wall). If you can't give him the money no strings attached, then don't give it at all, starting from the next academic year. Pulling out halfway through the year is VU.
If you use money as a weapon against him, especially without talking to him about the problem first, then he'll resent you for it and it'll take him a couple of years longer to come and start talking to you. If you say you're going to change the amount of money you give him and talk through your reasoning for the change, then that's probably not going to make him hate you.
Saying "get a job" is great, but have you tried getting a job recently with minimal qualifications, especially when you can't work certain times due to uni?
pretend he has a student loan totalling 5000/year, rent is 300/month = 3600/year, transport to uni is 10/week for 30 weeks =300/year (what money to give him during summer holidays will be up to you) then he'll have 5000 - 3600 - 300 = 1100/ year surplus from his student loan to live on. 30 weeks at £60/week = 1800 needed, so I'd advise giving this fictional student 700/year. Either in 1 blob at the start of the year, or as pocket money each week, or /semester or /month, depending on how mature he is with money. Since people normally get paid monthly, I asked my parents to give me money monthly.