Not exactly your question. but, from my end...
All of my guns are .22 cal. The end use should be similar. Unless your .25 pellet is over 50 or so grains in weight, your "low" power (?) should be just fine for accuracy up to 25 or 30 yrds.
Yeah, I've tuned all of my guns (the tuneable ones) to about 800fps. I don't shoot to 75 or 100 yrds, so I don't need the power, and see no sence in beating up the guns internal parts with a higher pressure than needed.
Plus, you may notice the UK. "don't" get the power (pressure) capabilities' that we in the US do ! Their max. is much lower than our max. power, and funny thing, they are still...accurate !
The 800fps that I use is just fine at 25yrds up to 25grn. pellet weight.
Oh yeah, all of my guns are also, like yours, shorter barreled.
Hope that helps some.
Mike