I have no service in Bahrain and have followed previous advice from the forum to no avail

[#1]

O2 doesn't have a PAYG roaming agreement with Bahrain.  You will need to buy a local SIM card or rely on wifi hot spots.

http://international.o2.co.uk/internationaltariffs/travelling_abroad

[#2]

Thanks davidj63,

My text messages are getting back to the UK okay (as are imessages but I understand the reason behind that).

Is this information available on the giffgaff site anywhere?

[#3]

Information about where giffgaff does not work is unfortunately not available from giffgaff - the O2 international page referenced above is the best information you're going to get.