I suspect one reason the curry restaurants are whinging is that a lot of them pay their staff very poorly, but the Bangladeshi staff can't speak English so have no way of complaining to the authorities.
This migrant shortage story is dragged out every few months but frankly there are so many indian / bangladeshi restaurants or takeaways there really would not be a problem if a few closed down anyway. We have just had another 3 open up in my local high street alone (there are already about 11). The problem certainly is not bringing in more migrants rather utilising those already here? And if they don't want to work in those takeaways well then realistically, it's goodbye takeaway.
The rice harvests are becoming subject to export control so the producing countries can meet demand at home. This is not going to change with a few good harvests.