I can see that the recommendation of the take over offer will...

I can see that the recommendation of the take over offer will have two effects on share price:
1. stop it from falling as buying below 20c will be attractive as will almost guarantee a profit
2. stop it from rising much, as why would you buy above 20c to then be sold off at 20c in ~6 months (unless you believe there will be a higher bid)

A lot of holders will simply sell out at 20c - rather than waiting ~6 months, so this creates a perfect opportunity for someone to accumulate a lot of shares at around 20c without a significant increase in price.

Seems someone is trying to do that from the 5M and 2.5M buy orders, will be interesting to see what happens in next few days