It was indeed Digweed in goal (don't forget he joined us in January 1981) - pic from that game which appeared in the home programme for the Arsenal match a week later:-
And the Arsenal prog also confirms that there was a TVS film crew present:-
Impressive memory - I was at the game and...
Correct. Looking at the programmes on Hiney's excellent Seagullsprogrammes website, the deal was announced in the prog for the Division 2 fixture against Portsmouth on October 8 and Phoenix Brewery shirts were worn in that fixture for the first time. The deal was worth £30,000 for the season.