If there's one thing I've learnt with new utilities connections is the first job the lads do when they arrive is look for a reason they can't do the job. For that reason I'd be trying to follow their spec. However gas seem the best of the lot I think cadent have incentivised them with bonuses per job over last few years the lads seem a bit keener.
I put in 4" yellow duct on last connection which was solid. I drilled it all over with 7mm bit as it was a short length of duct I got for free saved me buying a roll. Inspector came out, showed him drill holes, told him I could dig down anywhere on it and there would be holes. He told me it was most likely lads would walk off site on connection day. After he left I dug back on both ends of the duct, fired sone 63mm perf inside the 4inch, then bsckfilled both ends. Bloody games you have to play.