Money to spend. What to buy?

So I have about 150-200 quid and I cant decide between:

• a new helmet (probably a Spesh Prevail or Kask Vertigo)
  
• a new chainset (probably a 6700 Ultegra, maybe a Fulcrum racing torq)
  
• new shoes (probably a pair of Sidi ergo 3s)
  
• new bars, grips and levers for my brompton
  
  

what to do!?

I'd go with whatever would provide you the most result across the board. Are you gonna use the shoes for all your bikes, or just one?