......and breathe 
Firstly, if he is on a full loan, then he will be fine. All my dc have noted that their friends who are on the full loan seem to have the most disposable money.
If he can get accommodation for £5K ish, that leaves him over £4K for everything else. That is around £100 per week whilst he is at University. (If you are not charging him board in the holidays). That is more than twice as much as he will need. Honestly. I bet you don't have that sort of spending money ? I know I don't.
Now, depending where he goes, student accommodation can be in short supply and you don't always get first choice, so some students do end up being allocated more expensive accommodation.
However, you say he is used to working and also has savings and will also get some spending money from Dad and Grandad, so it sounds like he will be a lot wealthier than most of his peers.
Re the job - Supermarkets might not be glamorous, but they pay a lot better than hospitality - tell him my dd works in a bar through the night (finishes around 6am) and gets paid £6.56, and they have been told they will be sacked if they keep any tips ...... up to him of course, they all find their way.
House share costs do vary, but each of my dc (3 different Universities) have generally paid very similar to their rooms in halls, when they house shared. Some seem cheaper at first but you have to pay bills on top. Some include bills, and don't tend to be that different from halls *unless you've had en-suite in halls or otherwise expensive halls).
When you apply varies one university to the next. Most commonly (but not in any way at all) you apply after you have "firmed" which university you hope to go to. It will say on the website when it opens - can be anytime after about March, but sometimes not until May. Most don't allocate until after results day, but some now do. I think Nottingham is notorious for having a mad scramble on the day halls open (and Nttm is also very heavily weighted in catered halls for some reason). So you need to look on the accommodation pages for each University as they are all different, and more and more universities have privatised their accommodation now.
Yes, there is a deposit to be paid for, when you are allocated the room - usually a week or so after results day, and usually about 4 weeks / £450 ish. After that, it is paid termly the day after the loan comes in.
However, one surprise is you usually have to choose and pay deposit for 2nd year accommodation before Christmas in first year.
There is lots of information on UCAS website
There is lots of student finance info on Martin Lewis page
There are lots of worried parents (and helpful, experienced ones) on a Facebook group, and website, called WIWIKAU *What I Wish I knew About University)