For going to 1st floor only, I would go for 3.5m doubles.
Some people swear by pointer ladders, (ie those that the top section go to a point) so it can nose its way into corners when set. I never really got on with that type, but I'm sure they are very good. They're also called "Window cleaners" ladders.
You will need TRADE DUTY ladders, not domestic or light duty. Take my word on this, yes they are more expensive but MUCH sturdier.
I have bought ladders from ScrimCity and also Lansford access, both are good. Google em you'll find em.