DD exclusively had expressed breast milk until 5 months and i used the Avent Isis as I'd heard the medala are very noisy. Because I expressed a lot all of my friends have been with me while I've expressed and all of them who have had a medala have commented on how quiet mine are.
However, at 5 months (ironically as I dropped a feed that I was expressing to give me more time) I decided to call the NCT breast pump person and ask for advice. They recommended the Ameda lactaline dual breast pump. It costs the same as the Avent (£85) but is a million times better! It can be used as a single or double pump and double pumping saves a lot of time. With the Avent I had it on full suck but with the Ameda I had it on half way (and half way was more powerful than the Avent) so it goes all the way from really really gentle to suck your boobs off!
It is just as quiet as the Avent. I bought it from here:
http://www.simplybreastpumps.com/product/17071UK
There is an american website somewhere that did indepth study into lots of breastpumps and the ameda one is one of the few that are really effective according to them. Though in America it is called the Hollister Purely Yours. It took me a long long time to work that out!
http://breastfeeding.hypermart.net/pumps101.html They also recommend the Medala professional grade ones but that costs £200 as opposed to the £85 for the Ameda.
However, if you'd rather use a manual pump, the avent isis manual is far easier on the wrist and angles better than the Tommee Tippee one.
In my experience an electric one is better because you express for half an hour or more at a time and my mind would start to wonder and I'd realise I'd stopped expressing. With an electric you just plug in and let it get on with it
If you get the dual pump that halves the time. Turn it on, put one pump to one breast. Now hold that pump with the opposite hand. Put the other pump to the other breast and you will be able to hold it there with your first arm, leaving you a free hand to drink tea and change the TV chanel.