problems usually depend on the way the vehicle was used and maintained... a badly looked after / abused petrol car is no better than a diesel, in my experiences..
..and I wouldn't rush into an overhaul, unless I really really have to... it has a probability to give post overhaul issues.. besides, if there's no issue, why try fixing in the first place
Petrol and Diesel vehicles of same class usually don't have major differences in maintanance costs... this again based on my experiences...
As for SB14 and Bluebird, assuming U mean the U14, both have same engines and are fairly economical...
CE 110 and the Gallant are great options to consider as well...
Good luck with the search