Generally there are no requirements in the building regulations to consult your neighbours, but it would be sensible to do so. In any event you should be careful that your proposed building work does not interfere with their property as this could lead to bad feeling and possibly civil action for the modification or removal of the work.
For example your work may comply with the building regulations but could result in the obstruction or malfunctioning of your neighbour's boiler flue.
You should also check your boundary lines and satisfy yourself that there are no deeds of covenant which may prevent you carrying out certain types of building work close to or directly adjoining your neighbour's property.
If your project is subject to the Party Wall Act 1996 you must give notice to the adjoining owners under that act.