You're asking how long is a piece of string really - there are ways and means of seriously shaving the expense but in doing so you have to question yourself as to what you want to achieve - an MOT pass or a car returned to fine fettle that will last for many years if taken care of. If I were in that posiiton it would be the latter as to my mind if a jobs worth doing its worth doing properly once....
I'd reiterate my earlier view - that it'll be worse than you think - get a worse case view from an expert....not a "plate and fill" outfit - you're after mini specific sympathies and understanding...
..... there are folk out there that do a remarkable job for very reasonable money - yes they do exist - I'm lucky enough to know such a being in this neck of the woods - but ..... you can't determine a timescale - far more lucrative jobs come first and classic restos are fitted around workload...and in my case heritage panels are a minimum requirement otherwise he won't play! - ask around, take recomendations and see other work done... you'll find the right person eventually....
A fairly decent rule of thumb I use when assessing whether a car's worth repair is this...... price up the cost of the OE panel (here a BMH variety), add double that for the work and add 1½ x the original panel cost for the paint...... add that up, mop the tears and blow the moths from the wallet - that may be overstating the case a bit but has served me well.....
Structural repairs will take a while.... use the time wisely to do your desired refurb work and beg , borrow , wheel & deal to source the remaining bits & bobs needed to put the car back together (once a car's apart a myriad of small and overlooked parts need replacing which add up dramatically) - parts are out there if you look hard enough, fish ebay, breakers, the forum etc etc.....
One money saver that's a no brainer - is don't change colour on respray - at minimum that'll mean your don't have to completely strip to the shell to get interior and exterior to match....
Edited by wile e coyote, 25 July 2017 - 10:29 PM.