GoT holds my attention because there are so many ways to control the ship, between aiming the guns, shifting speed, and changing weapons. Furthermore, the game is actually designed with these options in mind; making some rapid changes at the right time can really make things at lot easier. For example, I change speed way more often in GoT than the Soldier games.
£22/$35 shipped for the PCE version seems a little high. If you're spending that kind of money I would have bought that U.S. version w/o manual for $40 (shipped) to get the extra games.
It's cheap by eBay prices, but I collect Japanese PCE Titles, and I think I already have the extra games (Unless the Air Zonk is "Super")