Hi and welcome,
It is generally accepted that BBC1 Channel Islands and ITV1 Channel Islands are the strongest (free to air / Freesat) BBC1 and ITV1 regions for reception on the Costa Blanca.
For BBC2,3,4, ITV2,3,4, C4 and Five the postcode does not make any difference in reception - as there are only one regional version of these channel on Freesat - and you will not get BBC2,3,4, C4, Five 24/7 where you are. (A Sky box with a sky card can get C4 and Five 24/7!)
So ANY postcode from the Channel Islands (JE1 1AA) will be best.
Hope this helps
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