The Insideflyer TopCashback sign up bonus has proved quite popular on this thread, offering £10 or 1050 free Avios.

While not quite as lucrative, the good news is we have also now got an additional offer which applies even to existing members.

Sign up for the existing member offer here, and the next time you earn ANY cashback, you will be given a £1/105 Avios bonus on top completely free.

We describe this as "sort of UK only" as it technically relates to UK shopping. However, a lot of people from outside the UK have signed up and benefited, as there's plenty of non-UK shopping options (not least flights and hotels).