Not sure about picture messages but my Goan Sim is with Idea. Most Goans I know are also with Idea so it must be quite a biggie.

i always use idea when im there,,just waiting to get hold of a card so i can use it in 2 weeks time..i find they are the better and more reliable network from experience

The service providers in Goa are:

BPL MOBILE (BPL USWEST Cellular / Vodaphone Essar Cellular Limited - Vodafone - Maharashtra & Goa)
AIRTEL (Bharti Airtel Limited / AirTel - Maharashtra)
IDEA (Aditya Birla Group / IDEA Cellular - Maharashtra)

BNSL MOBILE (Bharat Sanchar Nigam Limited)

The first three have roaming agrements with all the main UK providers including T-Mobile.
BNSL does not have any roaming agreements with UK providers, and will not accept outgoing calls or texts from UK mobiles, but will accept incoming calls and texts.

More info at:
http://www.gsmworld.com/roaming/gsminfo/cou_in.shtml
Also most UK service providers have a section on their websites with lists of roaming partners service capabilities, coverage maps and rates. For the linked site above and most of UK providers there is not a separate entry for the Goa coverage, it is shown as part of the data for Maharashtra (MH).

Geoff you are a star - Thanks a million.

Now I know I can use Airtel I can send picture messages instead of texts saving me money and making everyone jealous at the same time lol

Thanks !