Odd questions...
You need to look at bathroom zoning as a first priority.
The isolator is usually placed outside the bathroom, but could be placed in zones 3 or outside of the zones if you really wanted. If the fan is an inline type, in a loft, the bestplace for the isolator is adjacent the fan - in the loft.
The fan will usually be fed via the lighting circuit, usually directly, with no additional fusing. I will say, however, that most install instructions do say a 3amp fuse is required! This is usually them trying to cover their arses. You could install an unswitched FCU If you felt it warrented it.
Height of the fan?? No regs say a fixed height - again, the zones come into play. A 240v fan, if placed in zone 1, must be protected by a 30mA RCD, and be IPx4 rated (or IPx5 if subjected to jets). If in zone 2, RCD Protection can be ommited, but the IP rating still stands. Zone 3 and beond - no restrictions.
The safest bet for a DIYER.......an inline type - not in the bathroom, so doesn't have to comply to the regs outlined in the 'special locations' part of the regs.
Sorry if my wording is crap - alchohole works wonders...
