Just got my HSMP approved today-yay. Timelines:
My letter arrived on the 10th of July
My credit card got charged on the 21st of July (9 working days after arrival).
Approval letter received 5th of August.

Never ever received a confirmation or reference number to say they had received my package.

Sorry guys, my mistake:
My letter arrived on the 10th of July
My credit card got charged on the 21st of July (9 working days after arrival). Must have still been drunk from Friday night when I posted the message:)

Hi there

It seems it takes around 9-10 working days from package arriving at home office till the credit card is charged.
My letter arrived on the 17th of July
My credit card got charged yesterday, 28th of July

Hope this helps anyone who is anxious about processing times for payments.