Yep, as above my understanding is it’s not allowed.
I’d refer to CAB in the first instance.
Also – even if it was allowed, I can’t see how a calculation would give 0.46p per hour as the correct amount anyway.
Statutory holiday pay is for 5.6 weeks/year (i.e. this is the minimum allowed). Regardless of how many hours worked per week, the minimum hourly rate if it’s rolled-up like that would be £6.50 x 52 (weeks in a year which you have to be paid for) / 46.4 (weeks you actually work allowing for 5.6 weeks’ holiday) = £7.28 and a bit.
But that’s irrelevant anyway as it’s not allowed. They have to pay holiday pay when he/she is actually on holiday – based on the average of the last 12 weeks’ pay (so they can’t say that you’re on a zero-hours contract, get you to work 40 hours a week and pay you for a lesser number of hours during holiday either).
IANAL (but am an employer who tries to play fair!)