definitely spend on the underlay - besides, felt-backed carpets tend not to be as sturdy as woven/hessian backed ones.
We couldn't afford the 80% wool twist we wanted (whole house needed doing), so we got the very best synthetic one we could afford - woven backed, twist pile and (v important to us) stain resistant and guaranteed as such. It's still looking great two years in.
Good laminate will cost as much as good carpet, so depends on your taste - I find carpet more forgiving to dust and crawlers.
We went to a local cheap-ish carpet showroom, and the fitting etc was much cheaper than CarpetRight, and they let us keep all the offcuts (handy for makeshift garden rugs etc).
Nowhere near Hull though!