Fence height regulations. Is there any leeway?

I want to erect a fence to the side/front of my house for privacy. At present there is only a low boundary wall between my house and the house next door.So I would build the fence on my side of the boundary wall.

I have exactly 3 feet in length along the side up to my gable. Therefore, to my knowledge, as this is the side of my property, I can have a height of 1.8 metres without planning permission. However the 3 feet of length gives me very little screening so I have planted a fast growing grisalinea hedge a bit further out front. But there will still be a gap of about 2 feet between where the fence would stop and the hedge begins and further planting is not possible there.

If I were to extend the fence even another few inches in length beyond the gable towards the front, could that potentially cause issues? Does the front of a property, where you can only have 1.2 metres in height, begin strictly at the gable? Or is there some leeway allowed? My neighbours are not very nice, so I prefer to play safe.

Any advice on this please? Thanks.

In theory you'd need planning permission and cranky neighbours might object if you just go ahead, that said a grisilinia hedge will easily fill in that 2ft back towards the wall fairly quickly. As it grows tie a few side branches towards the gap and it will fill it in even quicker. Is there space there at all for a pot for the time being with a single grisilinia in it? If you had the pot space you can buy the single potted ones quite big already.

I often see the higher wall sloped to the lower wall with the slope starting at the exact gable so I suppose that gives a slight little bit extra coverage!

Thanks Monbretia for your reply. I actually went today and bought two more grisalinia and planted them into a trough planter beside the hedge, which now brings screening right up to my gable. But there is still a serious gap of almost 3 feet where the sides and entrances to the two houses meet. I could get fencing there of 1.8 metres in height as the neighbour's entrance is 3 feet further back from my gable so it is the side of my house. But like you say, perhaps the grisolinia will fill in that gap over time and no more screening may be necessary. Erecting such a narrow fence may not be worth the hassle and expense. What do people think?

Grisilinia will fill out a fair old gap if left grow but it just takes time. They grow as big as trees if not restrained! Only danger is I lost all my grisilinia hedges back in the snow/frost of whatever year it was very bad. That said I still planted more and they filled out in no time.

Do not forget the party wall between the two houses are shared and you should have agreement with your neighbour. You do not want to damage foundations to your house and the neighbours house if too close to the properties. The neighbour or council can be challenging the installation. The neighbour may cut it back to the bear min on their side as it affects their own grounds as it grows and put the cuttings on your side to dispose of. If you put too much of a hedge you are opening yourself to others questioning why so much privacy and what are you up too. Also Theives love hidden front entrances. If is sheltered anyone could try to get into the house as no one could see what is going on.
. Bear in mind you need to have a peaceful life. Even if you do not get along with your neighbour you are setting out a bad stall.
Party walls at the front should not be any higher than 1.2 metres at the front no higher than 2 metres at the back. If you decide to put a large fast growing hedge or higher timber fence /panelling along the boundary you may find the council could demand you take it down.