Hey - thanks for all the tips and info !! How completely naive I am - I thought I could just pop along to a bike shop and they would check me out - for free !!! will get my bike out and do the things you suggest and see where I am !
Thanks for the advice !!
Haha, not at all. You wouldn't believe the difference between local bike shops. Some do a huge amount of stuff for free, others won't so much as look at the bike without charging. It is after all a business and they need to pay staff etc. sometimes new bikes come with a free bike fit and also a free first service, maybe check that out with them.
On the home fitting front, if you try the steps I mention regards seat height, just make sure you can reach the pedal with your heel and don't need to tilt your pelvis in any way to do so, rocking from side to side to reach a pedal stroke is bad news.
So, bum flat, back straight (not bent to one side or another),leg extended, no bend in the knee = good saddle height...ish.
If you want to adjust anything else, like how far forward or back the seat is, then let us know, there here are a few home brew methods (involving a piece of string and a small weight) that will ensure your seat and knees are in the correct position.
Having said all of this, I am mindful of your original symptoms. A painful outer foot suggests I'll fitting shoes, or perhaps poor foot alignment. Decent shoes, with a clipped in position could help. Dodgy shoulders suggests incorrect headset/stem position but could also mean your saddle is tilted. So make sure the saddle is parallel to the ground. When you then lean forward to reach the hoods of the bars (the bits over the brakes), then your elbows should be slightly bent (not locked) and your shoulders loose, not hunched.
Personally,I suspect the shoulder issue is quite simply a case of getting used to having to raise your chin to see where you are going and is placing a new pressure on the back of your neck. MTB's offer a more upright ride style, so this change will doubtless make your neck ache at your shoulders...for a while.
If I carry a heavy rucksack, I still get a ache in my niche today.