I'm more than happy with La Senza - resized from 38B to 34B at a glance (but confirmed with tape & fittings). Our M&S only does appts for fittings and it seems only then if Aquarious is rising in Leo, if you know what I mean! I do agree with Peagirl though - it depends on who does it but I'd personally expect a specific lingerie shop to potentially have higher training standards than a store with a lingerie department.
La Senza is terrible for bra fitting and M&S didn't come out much better in the report I read. And don't go to Evans where they measured my friend standing in the middle of shop floor! I would really recommend going along to a bravissimo store - I was really surprised how tight the bra strap should be around the torso for a good fit but it has made a huge difference. I was wearing a 38D and they said I should be a 34F - a good fitting bra will really change your life
I like going to Debenhams, but then you've got the issue of some of the bras can be quite dear. I think sometimes it can depend on your size though, I'm a 34H at the min and if anybody tries to come near with me with a tapemeasure I get annoyed because it's inaccurate with bigger sizes. I've never been in a bravissimo shop because there isn't one near me.
You need to watch that they should check each bra when you've got them on, even after they've determined your size in one style because different brands etc can be different sizes.
Oh, and don't get fitted in mothercare!! I once asked them to fit me and she used a tape measure... over a big fat wolly jumper and tried telling me I was a 40D (doh!!)
Both M&S and La Senza have been great to me in the past. They are both very helpful. In M&S when they find out what size you are they bring you a nice selection of bras to try on.
I find that in M&S I am one cup size smaller than La Senza. And I find that M&S is better for more sensible (but still pretty) bras - like the ones without the padded cups and La Senza is better for party bras which give you a bit of oomph!
Bravissimo all the way. Mothercare measured me for a 42dd when I had just had my son and I got back ache and shoulder pain. I went to bravissimo when I wa in Brighton one day and I was measured a 36h!!!!!! And I have never looked back.
Apparently mothercare compensated on the inches over cup as they don't go higher than a dd so to get a sale measured me completely wrong!