Refurb or renew?

[straas]

No such thing as "life expired".
Why would you trigger 'us' by presenting an image of a dirty post-ride bike?
If you want new stuff just do it. How do you think we can reasonably give valid 'is it worth it?' advice? Chat. Chat.
Saddle - why?
Grips - probably but they're consumables, really.
Brakes - why? Are the rotors too thin? Are the calipers not functioning? Both? Pads OK?
Chainset - are there any 'fail' symptoms? What? Replace one or more rings if there is reason to. BB?
Fork (only one fork on a bike) - the problem is? You know whether you have the competency to service the fork. When's the last time you did?

Saddles worn with padding exposed so it soaks up water. Brakes can't be serviced because the drain valve for the fluid is rusted, gears skip under load because of wear - so those parts all need replacing as the can't be serviced. Fork could potentially be serviced but the cost benefit might go towards replacement when mechanics hours are accounted for.

 

[Ajax Bay]

If your chain is slipping (under load) then likely it's not the chainset.
More likely chainset is fine and a new cassette and chain are needed.
Good luck.

 

[fossyant]

Banana Industries have got SRAM front and rear 4 pot hydraulic brakes for £35 a set.