Trench Sizing

I have just received a Burburry trench coat. I'm not as confident in the sizing as I was when I ordered it. I'm a 42R [at Marks and Spencer anyway] and the coat is available in a 41 or a 43 inch chest measurement - so I went for a 43.

Can trench coats be tailored readily? If anyone has had adjustments made to theirs I'd be grateful to hear about it. If I could choose I't want it slimmed a little and shortened by a couple of inches - I'm 6ft and a smidge and pretty chunky, and the coat covers my knees [just].

My assumption is that with a suit a 41 would probably look silly, so it is better to be slightly too large than too small?

Trench in question:

M.

Thank you both.

I've been collecting design 'classics' this past year or so. I'm pleased with the quality of manufacture of the coat [made in England!] and the detailing - just the size that gives concern. One of my physical deformities is very long and short calves, so I may have it taken up above the knee if that is feasible.