I personally have a Bose A20 (flying a 757/767) yes it's expensive however I bought it as an investment to protect my hearing. I'm in this game another 30 years, but less if I'm deaf.
However I didn't buy the Bose straight away because there was no way I could afford it from day dot.
Several disadvantages of the QC15/ uflymike.
1) Not TSO approved. Not that relevant in the UK, but your employer may object.
2) The mike is on the wrong side for an FO. This makes it very difficult to use "uncupped" when your left ear has to be free. Particularly relevant during startup and during cruise when talking to flight deck visitors (cabin crew bringing you coffee and coming for a natter)
3) when the batteries run out it is unusable. If the batteries run out on an A20 it still works as a non noise cancelling headset. The qc15 stops working all together.
All that said as and when I become a captain I will probably buy the uflymike/qc15 combo and sell my A20 on eBay.
One final reminder for the A20. Again UK only. If your employer does not provide you with a noise cancelling headset HMRC allow you to make a tax claim for the capital expense.
If it were up to me either wait for a year or two when finances are better and bite the bullet for an A20 or make the investment now. In 30-40 years you'll thank yourself.