I changed my mind and decided to do a Cromwell for the Korean War instead of the Churchill, which kit I disliked. Trouble is, I plan to do the Accurate Armour C to E conversion, but this is the first time I've done anything like this. Has anyone done this already? I'd like to know more.

Sorry, C to F. And I got the parts. The directions are rather vague though.

I haven't done this conversion, but it looks pretty straight-forward. Cutting up the plastic hull is scary though! I'd cut the driver's hatch area a bit small at first, and file it back until the resin part fits - you don't want to mess around with too much filler here. Adding plastic strip on the underside of the opening to form a ledge helps make the resin hatch area more secure too.

The rear deck is another story - others whose builds I've admired have avoided cutting (and weakening) the hull by moving the hinges and re-scribing panel lines (using the resin part as guide)rather than splicing in the resin part. The changes are small enough, and the result has all the strength of the plastic part without the inherent weakness of a superglued joint for the resin. I've done this myself rather than buy a resin conversion, but it all depends on your scratch-building skills. If you do cut out the plastic deck, be careful how it all lines up when the upper hull/fenders unit is added to the lower hull. The Cromwells I have built all had a slight warp that meant the upper hull needed clamped in place, so do this before gluing in the resin deck.

Hope this helps!

The easiest way how to convert Tamiya C hull to F hull is to avoid buying that and any conversions and go straightforward by buying SKP Cromwell Mark IV and if wider tracks (15,5 inch) are needed then SKP tracks too... The model itself is fine multimedia build (keep in mind, it's a shortrun, main parts in a bit softer plastic, some details provided as PE and some of them in resin), with quite a few kick out marks to be filed or sanded, the tracks are not so easy but time consuming. Amount of money is different, I would say SKP Cromwell is pretty cheaper than Tamiya Cromwell plus AA conversions (you need at least two of them to complete tank in the latest configuration). And SKP tracks contain correct sprockets for 15,5 inch tracks.
My experience with AA conversion of Tamiya Cromwell to make Charioteer (the same amount of surgery to change driver's hatch and engine deck) is.... err, I made it, I even can say I enjoyed all that cutting, fitting, sanding and building but have to say it was not easy and I dropped their tracks, which were strange and sprockets did not look well when compared to pics of real Charioteer.

Thanks. It's for a Korean War Cromwell so I hope the conversion will still work.