Or just withdraw the cash from a hole in the wall, walk into HSBC with Sarah's bank details and ask to pay it into her account.

 

They'll make you fill out a paying in slip (whichtakes 30 seconds, if that) take the cash, stamp the slip and give you a receipt. The receipt will be stamped with a till number which you can use as a ref number with sarah cos the till number shows up on her account details next to the payment

 

there ya go!

 

easier than my ex, and more satisfying too!