*nods* I do understand - I wouldn't suggest that you go and have regular lessons what with all you already play and with going to uni etc - it's great to be able to play something for fun and a bit of light relief and not to be tooooo worried about perfecting it or having to be able to do this or that *right now*... however... I would seriously recommend having even just one lesson with someone who reeeeeeeeeeeally knows the flute and how to play it.
Even if it's the only lesson you ever have, having someone with a lot of knowledge and experience (which is why I would suggest a very experienced flute specialist who will see any major things or indeed minor things you might be doing wrong) listen to you play and look at what you are doing, and give you a few basic pointers as to the good and bad things you're doing and some simple tips to improve it, could really help you to play better even if it's only better at a level that's not as advanced as your other instruments.
It'd be a great idea to arrange a lesson and explain to the teacher that that is all you want - that you plan to do flute for fun and may or may not take it seriously in future, but all you want is to know if you're basically doing it right to start with - and have them tailor their advice accordingly (you don't want a teacher to say, oh well you should be doing 3 hours practice a day or something else obviously not applicable to you at the moment... there are only so many hours you can be blowing your lungs out!). A good and sympathetic teacher who has been thoroughly prewarned that sax, clarinet and piano (any I've missed??! lol...) are by far your majors and you are not planning to take up the flute seriously
now should hopefully be able to say, "This is great, keep it up, this isn't, this is how you can improve, go away and have fun!" and hopefully give you a few tips which can be implemented without going mad and practising four hours a day! If you ask around either at uni or at home you may well find out about teachers who, while they probably have full lists as regards regular students, may well be willing to give a consultation and help lesson to someone who may be a novice flautist but is also obviously an accomplished musician & therefore needs flute advice rather than trillions of lessons.
Even if you never get serious on the flute (and although many people change without having a problem, a fair number do find that single reed and flute aren't the most compatible at the highest levels, so it's probably sensible to give it a back seat right now?

) it may give you just that edge to know that your tone ISN'T such a weak point any longer, and if you do at any point (even in 20 years!) suddenly decide to take the flute up with serious intent, established good habits will give you a great headstart!
Anyway... I'm kinda waffling (you guys are pretty used to that, right?!

) but in a nutshell: 1) don't feel that I'm saying "you must", but I would suggest you keep it in the back of your mind as a possibility... and 2) don't ever feel that just because you're not taking an instrument all that seriously, or simply don't have the time and money to have regular lessons on it as compared to say the sax which you are way more advanced on, that you can't have a lesson or two and get a little advice, even if it's the only lesson you ever have!
I do hope I made sense and this is somehow useful... if not then just ignore me *grin* but I hope it did kinda add up...