It was a 1 player unit and was definitely during the £8 or £10 era, maybe £15 at a push, but I don't remember it being a £25 machine originally.
The sound when you got the feature was a voice singing "Go ba, Go bananas!"
Did either of those machines have the hidden feature i was talking about involving holding all 3 reels? Pretty sure the machine I am thinking of was a lot less colourful. It had a strong jungle dark green theme to it and was quite plain.