Hello Simonj123,
OSPF is a routing protocol and should be used to route between different IP subnets.
If your network diagram is correct you have duplicated Vlan-ids 10, 20 on switch1 and switch2 (and this wouldn't be a problem), but you have also duplicated IP subnets associated to the Vlans 10,20.
Both vlan10 and vlan20 are associated with IP subnets 192.168.10.0/24 and 192.168.20.0/24.
You cannot use a routed L3 link like the serial link between R1 and R2 to extend the IP subnets between the two routers.
A router is a broadcast firewall it stops the broadcast of a subnet associated to each connected interface or subinterface.
R2 and switch2 could still use Vlan-ids 10 and 20 as they are locally meaningful, but the associated IP subnets must be different like for example 192.168.30.0/24 and 192.168.40.0/24.
If you perform this change you have a correct IP internetwork and you avoid the issue of duplicated IP subnets.
At this point OSPF would allow communication between subnets
192.168.10.0/24, 192.168.20.0/24 attached to R1-SW1 site1
and
192.168.30.0/24, 192.168.40.0/24 attached to R2-Sw2 site 2
R2 OSPF configuration has to advertise the correct attached IP subnets
192.168.30.0/24 and 192.168.40.0/24.
As a final note, your current configuration could work only if between R1 and R2 would be possible to perform bridging instead of routing or using a more complex feature like L2TPv3.
The point is that you need to understand that routing works only between DIFFERENT IP subnets and cannot be used to extend/connect same IP subnets.
Hope to help
Giuseppe
