It's not widely known, but you can log into your Heathrow Rewards account and convert Lufthansa miles into Heathow shopping vouchers. It's not a great conversion rate but if you have some orphan miles about to expire, it may be your only option. Minimum conversion rate is 7500 miles = £20 voucher. Increments of 1875 miles will give you a further £5 voucher. Go to 'My Rewards when you log in, and then '£5 airport shopping vouchers'. Vouchers are delivered to the address registered to your Heathrow Rewards card. It's rather a shame to get rid of them this way but I am some way short of Lufthansa's 17k award for transcontinental business class within the US... and it's going up to 20k soon.