Electric Ireland requires me to accept all cookies to pay my bill online - who do I complain to?

Right lads, maybe a bit petty, but this is pissing me off. We just got an updated electric bill (in a rental, with a smart meter, from Electric Ireland). We're all supposed to pay ourselves online, but since we got our last bill, Electric Ireland has changed their website so now I have to accept all cookies in order for me to even get to the payment screen. I'm raging. I've tried just accepting the "functional" cookies, just the "performance" cookies, and the two together. Nope, won't work. Apparently I'll have to accept the "targetting" cookies as well. Now, I know they're tracking me regardless, but it's a bit of the principle of the thing. I feel I shouldn't have to accept any "non-essential" cookies for them to do what I've asked. Isn't there something in the guidelines about how websites can't require you to accept nonessential cookies for the core function of a page to be completed?