Just to qualify yesterday's reply a little as I was on my phone on my break at work......95s, if running standard stroke, and if there's nothing wrong, will easily make "full UK legal power" (plus a little), even in .177. As advised above, please firstly try the JSB pellets, especially the RS and Express variants, prior to undertaking any work to up the power. Likely culprits if it were down on power still........it has been short-stroked (maybe doubtful at this age - do you know its history?), the breech seal may be leaking, the factory may have fitted a spring that was too enthusiastically shortened for the UK or the piston seal is very tight and an extended period of running-in may have the desired effect.
Hope this helps.