hello mate and welcome
i also have a 1.6 ( the shame
) the mods i´d suggest are these,
* cold air induction set up, but a good one. bad ons will loose you power
* tuning chip / remap. this will be the quickest and easiest hp mod u can do
* cam swap, to something sharper .. 272 or 288 degree..
* porting and flowing the head, big money mod this one
* skimming the head, higher compression but not a good idea and also big money
* piston swap, also a big money mod , same result as above 2 realy. very good to combine above 2 and this one
* kompressor / charger unit such as dasc are widely recommended. high initial costs
* engine swap. not that hard depending which unit u choose. and luckily for you, england has no rules on cc displacement conversions
so go nuts
but, i´d get the rear drum brakes changed for 318 / 323 ti rear arms WITH DISCS!!!!
hth