Standard Offer Terms? Associate level

(UK-based job).

I've recently received a written offer to join an advisory firm at Associate level. It's not M&A (which I'm moving across from) but advising institutional investors (PE/hedge funds). I'm curious if some of the terms of my offer are unreasonable, namely:

• 6 months probation period with option for employer to extend a further 3 months
• Net 20 days holiday (i.e. excludes bank holiday)
• 6 month clause post-leaving not to join a competitor firm
• I "...will find details on company pension scheme during employment"
• Finally, I have 24 hours to sign and/or respond to the written offer

Any UK-based professionals want to share some thoughts on the above? Any insight greatly appreciated.