ok, i am an expert 
.
ive had and/or used the P&T, Marco Sky, Hoxton and Powertwin. if you want to cat me i'll answer any questions you have, but in brief:
Hoxton: is good budget option, solid. plenty of room in the back and comes with an insert to make newborn comfy. quite nice stripy pattern too. it is pretty heavy though. it is slightly longer than the Marco sky. pretty good value really, but mine is largly unused as my 2 older toddlers always argue over who sits where and i end up with baby in a sling anyway. (will sell you mine if you like!)
Marco Sky: good coz its small but 'not much legroom in back' is true. also, mine got kinda stiff to push over time. i gave it away in the end
Phil and Teds- a nice buggy. def useful, pleasure to push etc. lots of good points. one concern is that toddler in seat on bottom (in 2 toddler mode) keeps putting hands on the wheels, and then inevitably at some point into their mouths or eyes or nose, which is frankly disgusting (dogs piss etc) and potentially dangerous. i sold mine to justify buying another but i do miss it.
powertwin is luxurious, sure, but big and heavy and my 1 yr old in the front seat dozing off looked Very uncomfortable. pricey too.
have you ever seen one of \link{http://www.abcbuggy.co.nz/products.html\these?} the single 'everest' with a toddler seat on top? have just discovered them and have emailed them for details of where to buy/how much, so i'll let you know if youre interested.
and yes, i do have a compulsive pushchair buying problem. v v sad