What the platform has to do
Dormers, roof windows, raising a gable, getting steels in, and letting brickies and roofers work without living on a ladder. Rear access is the usual constraint on Essex semis: the garden, the neighbour, the side return.
Hire length
Plan in months, not days, unless the conversion is a very small Velux job. We would rather quote a longer hire with a clear weekly rate than take it down and put it back up because the carpenter overran.
Quick answers
Do I need scaffolding at the front and the back?
If work happens on both pitches, yes. A rear-only loft on a semi might only need the back and a side — that is a survey answer, not a website answer.