Excellent! Many thanks for confirming that, and indeed for making us aware of the problem originally :-) We'll roll out the change across all of our web servers so that no-one else gets caught in the same trap.
Re: upgrading your account -- the thing to look out for is the number of worker processes (which is something you can customize on the "Account" page). Basically, as requests come in for pages on your site, they're put into a queue. Worker processes pull requests off the queue one at a time, process them, return the result, and then move on to the next request (or wait for a request to appear if the queue is empty).
What that means is that if your site takes, say, 0.5 seconds to process a request, and you have two workers, you can handle 4 hits a second. If, instead, it takes 0.1 seconds to process a request, then it can handle 20 hits/second. If in the second case, you were to add on an extra worker, then you'd be able to handle 30 hits/second -- and so on.
If your site is doing Selenium stuff on every hit, then on average it will take quite a while to process requests -- so you might need quite a lot of workers to handle them. When I was using the simplified version of the site that we were talking about earlier, it took about 3 seconds to handle each request -- which would mean that if all views were like that, then with two workers, you could only handle a request every 1.5 seconds -- that is, 0.66 requests/second. To handle lots of traffic, you'd need lots of workers.
Of course, if most of your views are super-simple and there are only one or two that need to do Selenium stuff, then while those specific views might be slow, the average might be much lower than 3 seconds/request, so it wouldn't be a problem.
One thing to consider -- maybe there's some way you could move some or all of the Selenium stuff out of the website and into some other kind of code? For example, if students' timetables only need to be scraped once a day, you could do that in a scheduled task, and then put the results in a database or something like that -- then the website itself could just use the data from the DB.