I gave my 50th donation about a month ago. You still get a drink and biscuit, but at your donation chair (though this may depend on the donation centre.) I don't know if tea or coffee was on offer, as I don't drink either, but I know it wasn't when we used to use a local Mormon church as a donation centre, which upset some people.
There's loads of info on the website about the actual donation process. If you've been fine with blood samples at the GP, you should be fine with this. I have never had bruising from giving blood, but I have had from blood tests at the GP. I agree the plaster removal is the worst bit!
If you say you're a first time donor, you'll probably get a longer rest after and be watched a bit more carefully. But they've done a lot of research over the years on how to maintain blood pressure, which is why we're now told to drink a pint of water on arrival and do leg exercises while in the chair.
Do follow the advice about no strenuous exercise after- a chap at uni went and played rugby after giving blood, and fainted on the pitch. I did feel momentarily light-headed reaching up to a high cupboard after my last donation, but usually I don't notice anything.
I don't like being told where my blood has gone, but I know I'm in a minority on that.
So enjoy your afternoon out!