It is always a pain when there are several factors conspiring against you ! Sorry to hear about the big ends though, that is going to take more than a few minutes to sort out

RE plug connectors, I replaced mine with new ones ( reproduced by our friends in Mulbarton) and am very happy with them.
Re petrol, I use 95 French supermarket petrol every day in my R4's and have covered thousands of kms . I have never had any delaminating hoses in more than 8 years of R4 use, so I would be surprised if it was that. However I have just replaced all by fuel pipe on the Aprilia with the braided type, so will keep an eye on it , thanks !