Sagging in Mid Terrace Roof

[Damo74]

Hi,
I noticed a sag in my mum’s terraced house roof (Council built 1930s) - pic 4 doesn't show it very well but its quite pronounced. She’s 79/widowed and funds are limited so we’ve had a few assessments/quotes.

Sagging - We've had varying opinions and been quoted separately for 1) new roof or 2) jacking and bracing the purlin or 3) installing A-Frames.
All have said the roof is safe due to the supporting purlins already in place in Pic 1 so I'm just wondering if any work is actually needed (and they've said options 2 and 3 wouldn't visibly straighten the roof)

Water Ingress in pic 3 - one said re-rendering and replacing leadwork around chimney would sort this , another said just overlaying leadwork/flashing would suffice.

Would value your opinions

 

[Wayners]

Mate had his roof and timbers replaced around 2018 for £10.000

Same as yours and sagging


Yours has been replaced?.
Original slate and concrete tiles too heavy?

 

[Damo74]

Think she's had same tiles since moving in in 1970 - not sure about previous occupant

 

[Scally-Ho]

I've seen sagging all too often when old tired slates have been replaced with heavier concrete tiles, but without upgrading the existing timbers.