I have recently made three attempts to deal with various EU-level officers: two MEPs and two parts of the EU Commission. Here's how well they managed to deal with interactions from the public.
Elected official #1: Andrew Duff MEP
I wrote to Andrew Duff's office in Cambridge; the letter contained four quick questions, totalling no more than 75 words. Mr Duff is trying to revive the European Constitution, which has been rejected by the voters of two countries already. My letter languished in the Cambridge office for a couple of weeks, until I rang he MEP's Brussels office; no-one ever answered the phone in the Cambridge office. They managed to get Cambridge to fax them the letter, and sent me an acknowledgement. They undertook to respond to the letter, but didn't until I pestered them a few weeks later. I got one or two emails from Andrew Duff MEP himself, essentially insisting that his responses had already answered my questions, which in my opinion they did not.
Score: 3/10 - I'd rather an answer I disagreed with than a pretend answer
Elected official #2: Tom Wise MEP
I rang Tom Wise's office in Beds, and after a few attempts got through to one of his officials, who asked me to put my questions in writing by email. I did that, asking that Mr Wise put down written questions in the European Parliament about the democratic mandate behind two pieces of European legislation. I got an acknowledgement that this had been passed on to Mr Wise. I never heard anything more, but the two questions have since appeared, rolled into one, on the European Parliament website.
Unelected official #1: Nicholas Kaye (of the European Commission)
I was able to find Mr Kaye's contact details on the web and just phone him up. He was perfectly happy to give me fifteen minutes of his time discussing the quasilegislative proposal he's in charge of and answered all my questions. I didn't like some of the answers, but that's a separate issue. He gave me a useful list of names and contact details of the appropriate people in the UK government to speak to.
Unelected official(s) #2: European Commission's Freedom of Information staff
These people are in breach of their own deadlines on handing over documents I requested, and didn't even notify me of this. There are perfectly competent people working there, but they are at the mercy of the departments who actually possess the document you need. However they're difficult to get hold of, as they are often not in the office and have an impenetrable phone firewall which can't cope with the "who is the next most appropriate person to speak to if X is away?" question, at least, when not expressed in French.