The new company formed following the merger of T-Mobile and Orange is making some rapid changes. We have it on good authority that from some time in October, if you drop a call whilst with T-Mobile, your mobile device will, if the T-Mobile signal is weak or non-existent when you redial, seek to connect to the Orange network .
By January, roaming across the two networks should be seamless. It should also be possible from October onwards to be able to connect calls over the internet via your Broadband router.
No doubt, official announcements will be made in due course but if you are based in for example, North Norfolk and your mobile contract with Vodafone is up for renewal, it may be worth contacting Auditel for a detailed review before committing to a new 24 month contract.