I would guess that you changed it when following the suggestion in the first reply:
<form name="checkout_PP_LI" method="POST" action="https://www.PayPal.com/uk/cgi-bin/webscr">
To show amounts in pounds, put the following line in your checkout form:
<input type="hidden" name="currency_code" value="GBP">
I cannot test the checkout for you, I cannot place an order without being charged, you should create another paypal account to use for testing transactions.