Switching from Static to Dynamic IP?

Tl;dr - on old t static ip 350mb VMB contract at £62pm. Only use 2 static IPs, probably don't need to anymore.  Want the cheaper, faster deals.

Im on a grandfathered VMB broadband contract (350mb/5 static IP addresses) because in the past 1 of the services I ran needed a static IP. 

I've only ever used 2 (static) IP: 

1 for my home PC, 1 for this workstation 

Workstation no longer needs a static IP & im WAY overpaying £62pm for much slower speeds than current contracts 

What changes would I have to make if I switch to a new contract with 1 dynamic IP?

Quite honestly I just want to access the higher speeds for lower prices, and don't use 5 Static IPs

Since i only use 2 if i could access same deals but have/keep 2 static IPs that would be awesome but unlikely.  

Basically from the VM Router 1 line runs to my home (asus) router servicing the home network 

1 runs to the workstation router.  I realise workstation router will also need to be reconfigured as well as my home router to work via dynamic single IP but what else needs to be done?

Im guessing everything downstream of tge DHCP servers will work just fine & its a question of reconfiguration of the WAN details for the asus?

And also assuming ill have to swap out tge Hitron for a different VMB modem?

Too much to assume it can all be done remotely switching current static IP (to home router) as my dynamic IP?