Alternative to lead flashing - ikoflash

Are there any alternatives to lead flashing where a good seal is absolutely imperative.
I have to get 2m long section on a large rooflight flashed so its watertight. Roofer is telling me he needs to put expansion joints in and it will be hard to make it fully watertight.
Company which makes these agrees and suggest to use a product called ikoflash. Its supposed to be workable like lead but easier to use and no expansion. Anyone heard of it or similar products who can recommend this?

Sorry not heard of ikoflash, but have used and can recommend Ubiflex
Is available from most DIY sheds - there is a download available with all tech info and fitting instructions

http://www.gbplastics.co.uk/Products/Ubbiflex_lead_flashing_waterproof_ubbink_ubiflex

It is very ligth and easy to use, and provides a seal in exactly the same way as lead would.