I know its another 'tax the poorer members of society' type thing but ther is also this
https://www.3vcash.com/help-charges.html
basically you prepay and get a 'visa' number which you can use. the prepayment lasts for between 8 and 12 weeks and there is a small charge £3.50 per card which can be a value from £20 to £200(basically between 1.75% and a whopping 17.5% depending on how much you can afford to prepay). There is a admin charge if you don't spend it all within the period.
These aren't ideal but are one possible solution.
PS I genuinely don't mean anything derogatory with the first line, I know that peoples circumstances dictate things often well beyond their own control