tubular wheels and tyres ---help needed

[iansmyth]

Hi everyone whilst here in Moscow i bought a old XB3 start schosse  1970s edition , it has a nice set of original  XB3 alloy wheels 25 inch , i took the old flat worn tubes out and cleaned up the rims as there was a lot of glue/solution  from  the last pair,  on the tyres it reads 600 x 25 , ( i did get some spare tubes with these but alas they are 24 inch)  now i am having a bit of a night mare trying to finding something to fit these , i dont want to spend a fortune as the bike is not a master piece in the making and how can i tell the wheels are a 600?

any suggestions are welcome 

thanks 

Ian