How much more can I take?

Finally managed to finish the 8x8 album I've been working on for DS1's neice (she'll be one at the weekend) - pictures to follow (hopefully tomorrow) and spent the rest of the morning pottering on a layout for my class on wednesday night (yummy it is too!) before I was the victim of a random act of criminality!! This is how it goes:

A foreign couple come in to the shop & purchase (with a £50) a pack of rub-ons. I carefully consider whether I'm going to take this note - but I need every sale I can get so I take it & hand over £46 something in change. They then realise that these are not temporary tatoos & want a refund (the whole time talking away in a foriegn language & making sure I don't understand.) They even ask if I speak french, I reply (in french) that I do a little. The man then says something else (not in french, possibly italian - but I don't think so) So we swap the notes back except the change is now only £26 & I am £20 short. They don't even leave straight away - but browse some other papers (still speaking impossibly fast, this time I catch a couple of spanish words - but I don't think they were speaking spanish either!) They ask if we sell wallpaper - I do my best to get them out of the shop as fast as I can so that I can call the police. So maybe they think they are terribly clever & I don't know that they've robbed me - or maybe they are relying on the fact that I won't tackle them because I'm on my own - either way they win!!

So I let them (and my money) walk out of the shop. I am not rich & I cannot afford to lose £20. That is a whole month's electricity bill! It is not a victimless crime - my insurance won't cough up for £20 (the excess payment is £300!) and this is twice in as many weeks. I work seven days per week and most evenings, I take no wage AT ALL, every penny goes toward paying my suppliers, covering the shortfall for the six months we spent in a shopping precinct, covering the four months in which we had no premises. I have had just one day off this year & I expect my next one to be Christmas day.

I work hard to stay afloat & for what? For random criminals to come and help themselves? There are all sorts of attributive theories that I could apply: it's because I work in Dartford - well probably not, I suspect it's the same everywhere; it's down to the Eastern Europeans - well they might well have been Eastern European but I have other visitors from that area & they don't feel the need to rip me off! I could go on but there has to be a limit to how long I can vent my anger for (it has been, on & off, three hours so far) so maybe it's time to stop now.

So the burning question now is: how much more can I (or should I) take before packing the whole thing in & walking away?

Any thoughts?