I once blew £200 at the haberdashery counter in Peter Jones on samples and forgot all about it, lost the receipt, didn't claim for months afterwards, by which time my relationship with the accounts assistant (she called herself the accountant) had deteriorated to zero, so I ended up saying 'you know what, I'll pay for this shoot) which felt good for all of about five seconds afterwards.
I must tell my Mum that I know someone who spent £200 at the haberdashery counter in Peter Jones. She'll be green with envy. I think if she had £200 to spend at the haberdashery department in Peter Jones, she'd keel over from sheer excitement and indecision.
With regard to the OP - last year I spent £20 on a hi-vis coat for work, off York market, and didn't realise I could have claimed for it, if I'd got a receipt. Didn't bother me, I needed the coat, and it was cheap, and being a Small, it won't fit anyone else, so it's mine really, not work's. I bought some new steel toecapped boots today, I'll get the money for them, because I got a receipt.
I also use my mobile for short work calls sometimes, but I was told that in lieu of that, I can use the work phone if I need to at lunchtime for domestic odds and ends (and internet if I need to). I rarely need to, but I could. And we get free tea, and sometimes cake, and my tactic of collecting dregs means I won't have to buy washing up liquid for a couple of years...