K&N do a cold air intake for the Beeza 1.9TDI PD130 (ive got one on my car) sounds good but it can cause MAF issues.
 
Heres my milltek:

http://www.youtube.com/watch?v=7ZWevEs_Puo

Im really happy with it and would definately reccomend it over the mufferthingy, it is more expensive tho but i think theres a reason for that! Ive got the downpipe and sports cat which makes the turbo alot louder but im thinking of changing it to the non-resonated soon.

I also reccomend custom code because you can upgrade your car in stages and you get a discount when you get more mods and want a new remap. I think you should start off with the induction mods and a stage 1 remap then when u get bored get the milltek, fmic and a stage 2 remap.
 
Stu, if your looking for a better clutch, i had a sach's clutch fitted at JBS. The guys there are really helpful and the clutch is brilliant..... my Sport 130 one started to slip badly, i can now use all of my remap :D

Not sure what the going rate for the clutch is know.... you'll find JBS in the SCN sponsor list :)

and another mod you might need and is def worthwhile is the replacement of the front wishbone rear bushes from the standard 130 sport 'holey' versions to the solid cupra versions...... made a noticable difference to the ride and handling... the JBS guys can fit these as well.

HAve fun..... its a great little car the 130.