Yust looking at the site I would understand the "Non Refundable Security Deposit" is in fact a sort of damage waiver.
You either pay (for example) deposit of 1,500 EUR and take full risk (loosing from 0 to 1,500 EUR) or pay 450 EUR of which you never get back 225, but only pay 450 in case of damage (loosing from 225 to 450 EUR.
So does anyone have first had experience or is all just spaculation ?
Did you Britsailor check if perhaps it is not a scam afterall - and you said it is a trend - how many companies?
Not that I say we should blindly trust them - but let us give them a chance.
By the way - I chartered a lot in Med (mostly Adriatic), but never in Greek waters, so I have no experiance with Greek charter companies.