>>>also the seller had the inside label removed i wonder why ?
When chain stores (such as M&S, Next, etc) discontinue a range they sell off unsold items from that range to discount traders (such as QD Stores, here in eastern England). In order that those discount traders can't advertise the garments they're selling as 'M&S' or 'Next', the big stores cut their own labels out prior to selling the items. (You'll also often encounter labels having been cut out of garments if you buy from 'outlet' stores, where manufacturers or retailers sell off discontinued stock directly to the public, as well). So there's nothing unusual in the practice. (I bought a couple of sweatshirts, with the labels removed, from QD Stores just a few days ago).
If you return goods to an online seller by exercising your rights under the Consumer Contracts Regulations 2013 (which apply to all goods purchased, irrespective of whether they're 'fit for purpose' or not) then you have to pay the postage costs (although the seller is obliged to make that clear in his terms of business, prior to you buying).
If you return goods which aren't 'fit for purpose' (either because they're faulty or incorrectly described) under the Sale of Goods Act 1979, then the seller should ensure that you don't end up out-of-pocket by paying the postage. However the sizing of clothing is always a tricky matter because different manufacturers seem to measure in different ways. (The 34" waist jeans I'm wearing at the moment can't possibly be worn without a belt because they'd fall down straight away - but I've got other 34" waist jeans that require me to breathe in to do the button up!)