I went for my plasma donation this morning.
Turned up, did all the questionnaires and blood tests and vein searches and so on, all went well. They stuck a needle in and began taking plasma and all seemed to be going well, but the machine was beeping a lot. A nurse came over and got me to squeeze a plastic toilet roll thing to try and increase flow, as apparently the machine wasn't happy with how much it was getting out. Another nurse came and tried to adjust the needle, but instantly caused a bruise, so had to abort the donation unfortunately.
They took maybe about 10ml of plasma (which they said they will use), but I can't try again for 4 weeks because they didn't flush me out or something. I'm going to try booking in again in 4 weeks and giving the other arm a go. I got a nurse to check the other arm at the time and she said it looked viable, so we'll wait and see.
I'm disappointed that I couldn't do more, but I've done what I can up to this point I suppose.