Another Bug in rules PLEASE HELP

I'd really love to be proved wrong on this because its been the source of 2 days worth of head scratching now. Please help...

I am renting out one item. There is a pricing structure that gives better rates for longer bookings. From reading around the forum this isn't particularly unusual.

My rates:
Days 1-7 are £6.50
Days 8-14 are £5
Days 15+ are £3.50

So for example a 16 day booking would be (7 x £6.50) + (7 x £5) + (2 x  £3.50) = £87.50

So, as you may expect (hopefully) I have 3 rules:
1-7 : this rule has a max number of days of 7
8-14 : this rule has min / max days of 8 / 14
15+ : this rule has min number of days of 15

and I have 3 special events which each set a new price:

1-7 : this event uses rule 1-7 and sets price to £6.50
8-14 : this event uses rule 8-14 and sets price to £5
15+ : this event uses rule 15+ and sets price to £3.50

This almost works. bookings of 1-7 days are correct price, as are 8-14 days. But when I try a booking of 15 days or more, it just sets the all the days to be £3.50?!? so my 16 day booking results in a price of £56.... that's a loss that I can't afford or accept.

I've deleted everything and tried it all again. No dfference. I have even tried just 2 rules and events - 1-7 and 15+ and just using a base price of £5 for the 8-14 day class. No difference.

Please help, there must be a way!

Many thanks
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