Could someone help me out

It's July. Why are you working on this now?

On September 1st Tyrol Ltd, manufacturers of a muesli cereal, advertised in the national press that they would give a quartz watch to those customers who replied, to the address given, enclosing six vouchers from their cereal packets and a cheque for £1.50.

On September 8th Bert posts his six vouchers and encloses £1.50 cash. In the meantime Tyrol Ltd decided to withdraw the offer and have placed an advert in the national press for September 9th announcing that the watches are no longer available. By this date, Clive has collected five vouchers and does not see the advertisement withdrawing the offer.

Bert’s reply arrives on September 10th. Clive obtains a further voucher and sends six together with a cheque for £1.50 to the stated address. Clive’s reply is posted on September 11th and arrives two days later.

Tyrol Ltd now refuse to supply Bert and Clive with the watches.

Advise Bert and Clive.

I don't think Clive stands no chance. It's a unilateral offer and he's started performance (at least arguably) by collecting five of the vouchers before the offer was withdrawn.

You may be right. but performance is incomplete as he does not yet have all vouchers: nor has he submitted them before the offer has been withdrawn. Meeting all the conditions before the offer is withdrawn would achieve acceptance.

Yes, the point is that you cannot withdraw a unilateral offer vis a vis someone who has begun performance, see for example Errington v Errington, or Daulia v Four Millbank Nominees. If I offer £1000 to the first person to walk from London to York, I can't change my mind after someone has already got to Doncaster!