"Holding offers" in Clearing

You can phone as many Unis as you like but if a Uni has asked for your Clearing application and you have submitted it, then you you cannot do anything else unless you want to withdraw that application and start again with another University.

No you dont have to make an immediate decision if you are made an offer - but why did you apply if you don't want to go there?

As above, you can speak to as many unis as you wish, and you can hold as many ‘offers in principle’ as you can get - but these may be time sensitive and only valid for a specific period. You can only refer yourself to a single clearing choice.

It's my first choice, but being in clearing, it's first come first serve and as the course I'm applying for is rather competitive, I'd rather get an offer from a non-priority than spend time waiting for a priority and end up (potentially) missing out on both. This is the dilemma I'm in: how long do I wait before applying to another university if I'm already waiting for a reply from one that I'd prefer. And if I did get an offer from the 2nd choice, should I just take it? How long shall I/can I hold the offer for while I wait for a response from the other, top priority uni.

To be fair, your first clearing preference will try not to keep you hanging on. They'll be aware that you may be fielding other offers. There's no harm in asking them for approximate timescales if they haven't given any yet.

I asked them and they said I may have to wait up to 3 days. I contacted 2 of my other options and I was put on a waiting list - they'll call me back.

I'm very surprised at how long I'm expected to wait, I thought they'd make a decision then and there, or at least schedule an interview. I'm not going to be waiting around anymore.

3 days is reasonable during this 'early clearing' stage. They're not geared up with dozens of staff trained specifically to process clearing enquiries as they will be during A-Level results time. It's just the existing admissions staff taking them on in addition to their day-to-day activities; processing international results, enquirires, updating offer holders etc.

Courses don't tend to close suddenly at this point, because only a few applicants have their final results.

Ah so this is rather normal at this point, I see. I guess during results day in August when people can then accept or decline their conditional offer, that's when the floodgates open.