I'm looking to buy my first pair of reasonable headphones, and some of you seem to know about this kind of thing. I listen to very little music, and mostly want them for listening to soundscapes on youtube recorded with binaural microphones. At the moment I'm using a £10 headset; I suspect I'm missing detail, and am prepared to spend some money to find out.
I'm aiming to spend around £50, but am looking for value rather than cheap. My searching so far has led me to the Sony MDR7506 (£75) and the Sennheiser HD449 (£60). Any thoughts? One potential problem with the MDR7056 appears to be that they might provide extremely accurate reproduction of people's not-that-great microphones.
I'm familiar with both units. There are lots of reviews online for each of these, so google is your friend. Audio reviews are like wine reviews though (sound is subjective), so use them as a starting point, then arrange a demo of each at all possible. The good news is that your source material is accessible from your phone or tablet, or an in-store computer.
A few general thoughts: a) I think you are doing the right thing by looking at around-the-ear models. b) With around-the-ear phones, how comfortable they are during extended wearing is very nearly as important as how they sound (unless you only have them on for 3 or 4 minutes at a time). If you demo them, keep them on for at least 15 or 20 minutes (more on this in a moment).
In terms of features, the Sennheiser is going to be a little lighter in weight, but comes with a shorter cord. Sennheisers do not fold, the Sony pair does, if storage is an issue. Both are wired, with the cord attaching only to the left earpiece. That sometimes matters if you are moving around in a studio, at a mixing board, or similar. Sitting in one spot plugged into your computer it would be less of a factor. Ear pads on both are user replaceable and inexpensive. (This will matter only if you keep the headphones a long time, and either of these will last you a VERY long time if not chewed on by dogs or thrown about by kids).
The Sonys have been around since 1991. I own a pair of their precursor/older bother that is in the same price range in the US, the MDR-V6. Both Sony models are well respected headphones designed many years ago (1985 and 1991). They are very similar. The V6 has just recently been discontinued by Sony, so you may begin seeing it at clearance prices in your area. Full retail was about $100 here (67 pounds?).
Now I'm going to throw you a curve. You don't say what your current headphones are, but I can suggest/strongly recommend a VERY comfortable, very capable around-the-ear headphone for about $25 (16 pounds?) - the JVC HA-RX500. This is one of 3 pairs I own (the third pair being two orders of magnitude more expensive), and unless I am sitting down for extended critical listening, I reach for the JVC's first. Why? Comfort. They (arguably) don't have some of the strengths of the V6's, but they don't miss by much, and they are much more comfortable, so when I'm streaming Pandora for hours at a time while at my desk, I want them over the Sonys. At that price point, their value is enormous, and I don't think you can go wrong. They are almost guaranteed to be a step up from what you have, they will last a long time, and you'd get an answer to your question about source material issues without a huge investment. And in the off chance that you didn't like the actual headphone (for reasons other than source material), you'd still have most of your budget in your pocket to try one of the models you enumerated.
TL:DR - You can't go wrong with either choice, but given your concern about source material, a third option in my final paragraph may be an attractive option.
Edit: To eliminate a double negative, and clarify one point.