A few years ago giant connifers became the in thing, but became unpopular with neighbours as they blocked out light and views. The council regs state that if they are forming a boundary or hedge then the height can be no more than 2 metres (same as fences), or planning permission will be needed. Freestanding connifers (1 or 2 set apart) should be ok provided they don't cause a nuisance.
Regarding hedges to the front of a property, it depends on local regulations. I am in a "open plan" area, which means no high hedges.. I'm not sure what is allowed but a lot of people have small fences, etc. Give the local council a call, their phone number will be in the phone book (and on your council tax bill).. ask for planning dept.