Instructions:It's a little bit late, but while booking a holiday on the Thomson/TUI owned holiday hypermarket website, I read the terms and conditions and found this little bonus in the small print:
SAVE30 – Valid 21st July to 31st July 2014
Voucher valid on all Thomson and First Choice holidays booked online only at holidayhypermarket.co.uk. To use your voucher enter the code on the ‘Travel Options’ page to receive a £30 extra discount per booking. Minimum two people travelling. Applicable to new bookings only. You must travel between 22nd July and 31st October 2014. Vouchers cannot be combined but may be used more than once. We reserve the right to withdraw the promotion at any time. Minimum spend £800.
I confirmed it worked on our booking, I hope it helps someone else too