It seems like in spite of your best efforts you're getting crap ratings so may as well add a quid or so to make up for the grief?
I guess I find it too difficult to weigh some things accurately, like a baby carrier or a bicycle wheel, and then trying to get the packaging right....
the only way I could get it exactly right would be if I took the photos, then packaged the item up, then went to post office (I never feel 100% confident about weighing at home and then navigating the options on RM mailsite, especially for the quite bulky items I can't weigh accurately at home, anyway), stood in long queue at PO, asked for PO the postage, then went home, then could finally make the auction listing with the "true" postage value, then hopefully the item would sell and I wouldn't have wasted time and packaging materials, especially if the buyer wanted a local pick up, then back to the post office to actually post it.
Which is a lot of effort for something that only fetches a net profit to me of 2-5 pounds. That includes any extra p+p snuck in, so I'd be only getting 1-2 quid per item much of the time if I was determined about adding no more than extra 10p onto real postage amount.
(Does that 10p really cover the costs of things like silver pen and parcel tape?)
I have never ever before bothered to look at a seller's detailed ratings (for speed of dispatch, postage costs, etc), do most buyers check them? Guess I'm lazy! Checking my own now... No, I can't. I don't get to see them since I sell less than 10 items/year. Does anyone else get to see them, I wonder, if you're a low volume seller?
Maybe I'll see them in a month or sooner, I have sold a lot lately, seems like.