Can anyone perhaps advise what "type" of service 135000km would be on my Caddy 2.0TDi? The last service was a cambelt service, but not at the stealership, it's shouting for a service but not sure if it's a normal filters and oil service.

If you did a major service at 120k km's including cambelt, water pump, etc. then an oil and filters service will suffice unless you suspect needing more or there are issues.