Ye Olde Inn

Ok well as best I can tell, tiles in HQ are 2.3 cm. The minis used are slightly larger (problem in crowded spaces) and I don't know how uniform HQ minis are with other Citadel minis.

I am looking at making a modular tile set and am trying to settle on dimensions. Any advice would be much appreciated.

What we probably need on the board somewhere is definative list of HQ dimentions for everything. Board, Tiles, Miniatures, Cards, Furniture/Doors etc for both EU/US if different. I have heard slightly differing results of certain miniatures, and even card sizes (in EU cards at least).

If we can all form some kind of list for measurements, resources can be made just by refering to the master list/table.

HQ squares are 2.25 cm. Most Warhammer Fantasy miniatures (Citadel) are compatible. Personally, I'd increase the size of the squares to just slightly larger than the width of the HQ doors. A measurement in which I don't recall at the moment.

HeroQuest squares are not ... squares.
Some are 2,3cm² other 1,9 on 2,3 so the better way is to make it at 2,5cm².
It will suit to all figurines and give more space.
3cm² is too large and takes too much space. (cf Warhammer Quest)

I'm going to be so American here for a minute...

I think I used a space size of 1 inch by 1 inch. I'll have to double check. But I think that is just larger than
the HQ figurines, and so it alleviates the problem of crowding.

The squares on the classic gameboard differ slightly in size, but I just measured the overall length, divided it by 26 and calculated an average lenght / width of 2,27cm, which I used when printing custom tiles.
When you make a whole custom board (or tiles for a modular gameboard) then you are not restricted to the original size and could perhaps opt for slightly larger squares to avoid "crowding".