Contraflow:
Wiretwister:
Second paragraph is the relevant bit in my reasoning. The caller from the company is conceding that the prior arrangments are being honoured. This of course with the situation being as described in the OP
… saying I am being moved at short notice to Mon -Fri this week and overtime on Sat if I want it!! Otherwise I have a nice long weekend Sat,Sun,Mon off!!!
That’s next weekend. If he doesn’t work the Saturday, then he’ll have that plus his normal two days off. It doesn’t change the fact he’s being made to work tomorrow (one of his normal days off) at short notice.
Am I the only one that can read? 
Nope, that’s how I read it as well. Looks like he refused to work tomorrow as he has plans. It’s his normal day off and the company need him in so have coincidently changed his shift pattern for this week.
Don’t know what the OP can do about it. Depends on the company and how long I’d been there but I’d probably dig my heels in and tell them to ■■■■ off as I’d already made plans.
Contraflow:
That’s next weekend. If he doesn’t work the Saturday, then he’ll have that plus his normal two days off. It doesn’t change the fact he’s being made to work tomorrow (one of his normal days off) at short notice.
Am I the only one that can read?
That’s one way of interpreting the original statement but not the only way. I am literate and come to a different conclusion to you, as did mickeyblue. If and when the OP comes back and tells us what happened we will all know which one was correct.
When I worked for co-op they had to give you 24hrs WRITTEN notice of making you work you Rest Day. They also had to give a minimum of 4 weeks notice of a perm change of Rest Day/s.
I do not know if it was company policy but they would never budge from those rules, I had my Rest Day by force 5 times in 9 years.
They would also honour days for any plans you had on any days you would have been off (within reason).
You could always put a family friendly request in, they legally have to try to honour it and can only turn it down for business reasons if there is no one else that can cover it.
Bertie1973:
I currently work Tue-Sat…Rest Sun & Mon.
Had a call asking me to work overtime on Mon but said NO as have things planned with the family!
I get another call (VERY POLITE) saying I am being moved at short notice to Mon -Fri this week and overtime on Sat if I want it!! Otherwise I have a nice long weekend Sat,Sun,Mon off!!!
All this with less then 15 hours notice?? I am looking forward to my long weekend as have no plans to do O/T on Sat!!!
Just wondered what the rules are on changing shifts as I finished on Sat at 1730 after 5 days??
Well there’s your problem right there.
Don’t answer the phone or turn your mobile off when you have time off.
It’s called Haulage. Things change.
Some of the questions being asked nowadays? 
Where will we be in 20 years?
NewLad:
When I worked for co-op they had to give you 24hrs WRITTEN notice of making you work you Rest Day. They also had to give a minimum of 4 weeks notice of a perm change of Rest Day/s.
I do not know if it was company policy but they would never budge from those rules, I had my Rest Day by force 5 times in 9 years.
They would also honour days for any plans you had on any days you would have been off (within reason).
You could always put a family friendly request in, they legally have to try to honour it and can only turn it down for business reasons if there is no one else that can cover it.
Nail and head spring to mind. Trouble is trying to prove whether or not they can accommodate it.
Cheers for all the advice guys!!! Well I worked an 11 hour day and am now looking forward to Sat,Sun and Mon off after finishing on Fri!!! 
At least the SUN was shining in GLORIOUS DEVON TODAY!!!