Travel to Seville

[TomUK]

I noticed on Google Street View that there is a Tourismo office and rest area on the Algarve bound side of the road some way past the bridge. Another sign says 'Posto Misto Frontiera' and this complex is next to the tourist office and I presume you refer to this. Presumably, this complex has replaced the original small frontier kiosk which was almost at the bridge on the Spanish bound carriageway.
Actually, 'Googling' along back to Spain, there is a small cleared area of land just before the bridge at the side of the motorway with two concrete slabs in front it. This seems to be the site of the original kiosk. Once over the bridge and into Spain, they don't appear to have any frontier post at all.
The Google Street View coverage of the Algarve is surely imminent, but as of this moment you get a couple of miles into Portugal on the A22 and coverage ceases.