Mark Fletcher
Hi Peter, There are no wooden floors available that do not dent! Even the very hardest wood will dent with enough force applied. Oak is hard, but not as hard as maple, which is not as hard as wenge and so on. In terms of the difference between solid and engineered - there is no difference in hardness. Whatever wood the top surface is, it will be the same with either board. However, engineered wood is far more stable and less prone to cupping, distortion and movement (if fitted properly!). You can't tell the difference between the two once it is installed. I wouldn't recommend any floors from the retailers you mention - far better to go to a specialist wood floor company (you'll find plenty on Google) and you'll often find that you'll get a better made floor that is better value for money.
