I will stick with my 11% from Seker Bank.
I will stick with my 11.75 from TEB
I'm sure you will. However, the point of the original post was to point out that there are ways to make more than you're getting from Şekerbank or TEB.
Lets say you had £100k to invest one year ago today.
If you'd simply lumped it into Şekerbank or TEB at 11% and not taken out any interest you'd have made 48,247tl. Unfortunately, your initial investment is now only worth £92, 427. In lira terms, you've lost 34,078tl so your net gain is only 14,168tl.
If you'd converted your initial investment into dollars and did the exact same, with the lower interest rate of 1.5%, you'd have made $2,176 which equates to 7,898tl. However, your initial investment (after conversion) is now worth £117,073. In lira terms a gain of 76,828tl, which if you add your interest makes an overall gain of 84,726tl and your original £100,000 is still intact.
Obviously this is simply an example, and I haven't taken into account taxes or fees - if you'd left the original stake in sterling then your gains wouldn't be as much, but still more than you'd have made in lira. Its also skewed a bit by the strong pound from a year ago but the principle is solid, hard currencies hold their value, the lira doesn't (currently).
The whole scenario relies on a falling lira, which is what we've had for six or seven years now.
JF