we usually use deals for eurotunnel
and one yr we converted deals to airmiles,and booked eurostar ( you can also book packages and of course flights too!)
for our oct trip we used deals for tickets, think it was £27.50 per person for a 1 day hopper
but be aware that the tickets, and also airmiles deals are not a great conversion rate
and as of dec it's going to get worse, with deals going down to 3 x instead of 4 x worth