Be careful buying second hand as apparently this model was recalled because of a faulty handlebar and brake. Also you can't hang things from the handlebar because this is the brake.
Personally I had the Phil and teds e3 explorer and had multiple issues with poor manufacture quality. (brakes, rear wheel, rubbish thin tyres that constantly got punctures, mesh fabric in seat wearing through in a short time, harness buckles not being stitched in place (choking hazard to my 2y old!)....fabric footwell impractical as toddler could press front wheel with feet and randomly stop the pushchair (dangerous at times!).
Since then I owned a mountain buggy swift since they were taken over by Phil and teds, and this too had poor manufacture quality issues....I wouldn't recommend their products to anybody now.
On a more positive note, there are many other options out there. I love the babyjogger brand functionality and quality. Babyjogger proves to be durable, practical, a pleasure to use and simple to fold!
Micralite are bringing out their twofold buggy soon which looks great.
Why not have a look at some online reviews. Www.bestbuggy.co.uk is really good.

I believe the Dash is one of the worst P&T models. The seat is smaller (the Explorer has a much taller seat). When the older child is on the top on the doubles kit ie in newborn mode then the bar at the back digs into their head and the hood barely goes over. One mum reported the raincover in the childs face when on top. The handle drops down for the brake and can hit the baby on the head. Its the only P&Ts that I kick the doubles kit with my knees - and I wasn't the only one!! One shop I went to said that they would never recommend the Dash for a child over about 18 months. There is a review here

I agree that you need a double pushchair but personally I would suggest you look at the Britax B-Dual or a different P&Ts or even a Mountain Buggy +One.

Oh my goodness! Get well soon.