you should definitely complain about the missed delivery date, and the fake “signing” but the problem here is that depending on the contract the suppliers and UPS may point the finger at one another.
Start with the goods supplier as its their duty to take appropriate steps to ensure the goods do reach you, and make it clear to them UPS did a false “signing”.
any companies management checks can be overridden to meet targets if people high up enough with the right passwords/IT knowledge work together, unless you put in extra survillance/monitoring.
Also bear in mind that although £120 is a lot to you it is often peanuts to many companies revenue – that said most good companies will just sort out the problem and just redeliver if they feel it will secure repeat business.
one caveat about complaining too much is big companies also got where they were by knowing which customers to dump as well as which ones to keep, in many cases the customer is only as right as their potential spend and companies are a lot shrewder at working this out these days.
Also many reduce the compensation you get if you go to the press because they know it may encourage copycat claims (saw this happen when I worked in insurance).
A lot of places are fairly honest though, whilst doing year end accounts at my work I found a debit balance on a creditors ledger (this means that they owe us money as we have overpaid them!).
I suspected at least one invoice had been double counted and paid twice, and having checked this I got the purchasing manager to check with the suppliers. They actually found a second double counted invoice (from before the time I started with this company) and credited more money back to our account!
