I can answer the first part easily enough, will need to look up buses for the rest.
Patra to Pyrgos, up to 10 buses a day, then a local bus to Olympia.
Sites only in Greek, but here's the times (& return), should make sense, but if you need help just ask,
Patras-Pyrgos-Patras,
http://www.ktelachaias.gr/?module=default&pages_id=42&lang=el
Pyrgos-Olympia-Pyrgos,
http://www.ktelileias.gr/Site/39-%CE%A0%CF%8D%CF%81%CE%B3%CE%BF%CF%82%20-%20%CE%9F%CE%BB%CF%8D%CE%BC%CF%80%CE%B9%CE%B1
Next you want Delphi, can be done, but change of buses needed, then same again to Meteora (those high rocks!)
Before anyone tries to find the rest of the schedule how long are you allowing between arriving in Patras & getting to Croatia? It may not be possible to do it all because of schedule timing.

From Patras you can take a bus directly to Delphi,
here is the website of KTEL Fokidas ( It's the prefectute, where Delphi is located)

http://www.ktel-fokidas.gr/?module=default&pages_id=32&lang=en

Getting from Delphi to Meteora is more complicated..

You will take a bus to Livadia and from there the train to Kalambaka.
You can check it on line on :
http://www.trainose.gr/en

There are no international trains from Greece to anywhere, to get to Croatia you will have to take a flight.
Croatia Airlines was flying from Dubronik and Zagreb to Athens last year.

Joint effort Clausar! Too busy at the time to look up the other buses, thanks

I don't have a schedule or time restriction on arrival at Patra
I go to Olympia and see what I can
Ditto for Delphi and Meteora
Yes heard as part of Greece,s economic woe,s there
train service suffering big time
Would there be busses running across Greek border
and further north OR will I have to take to the air
Possibly Thessalonika there may be flights

I doubt there are busses between Greece and Croatia, there are regular busses to the countries of origin of many immigrants that are living in Greece, or where there are Greek students, Croatia is not amongst them.

Flying would be your only option i believe.
You can check on flights on every on line travel site, here's a greek one : www.airtickets.gr