Some already asked the question but I didn't see an answer, are building control involved in this? I certainly wouldn't allow the timber lintol, I would be sorting that out before worrying about the roof.
I'll take that as no I don't have any B regs? Lintol is to small and in that location will rot, I just wonder what if any foundations you have.
The op said the lintel was put in by a builder. I'm sure others said it will suffice even though a concrete one would be better.
Looks like your tough love payed off @Jord86 Credit to OP for following the advice on rafter size. Pitch looks better than before. Make sure to keep an eye on the headlap of the tiles, as someone said earlier.