Hi,

It is a little tight but given the following;

(1) Travelling in Exec first so you can use fast track immigration;
(2) Bags checked through to EDI ( if any)
(3) bmi boarding pass collected at departure

Then I would think you might just have enough time for a quick showr /bite to eat before leaving for T1.

I would leave the arrivals lounge1 hour prior to departure
Allow 10-15mins to get to T1 ( underground walkway)
Allow 10-15mins to clear T1 security
This woulg give you 10mins or so before they start boarding ( usually 20mins prior to dep)

Regards

TBS