Hi and welcome to MM
Technically, with sequential HRT ( as you are using), the period like bleed should happen a day or two after you finish the combined oestrogen with progesterone patches - so when you are back on the oestrogen only patches. It's called a ‘withdrawal' bleed because you have withdrawn/stopped the progesterone and this triggers the shedding of the womb lining.
It is early days for you and the HRT clearly hasn't taken control of your cycle yet - perhaps your own hormones are breaking through a bit at this stage. Sometimes patches don't stick that well so are not absorbing as they should, this can throw the hormones levels off and cause breakthrough bleeding at odd times. The problem with mucking about with how you use theses patches is that your body may not respond that well and you get further problems. Hopefully over the next 2-3 months your cycle will be under control and the bleed will arrive when it should. If, by May/June time, it still looks as though the bleed will arrive on holiday - get back to us and we may be able to advice a strategy to delay it by a week. DG x