You are probably looking at around £500 just for the parts to do the work you are planning.
The replies above about the bonnet lip are correct to a point. Yes it is easy to remove the lip but if the bonnet is not completely sound to begin with, then it will need repairs once the lip is removed.
Best case scenario is that the lip just Needs painting where the bare metal is exposed from removing the spot welds.
alot depends on the colour of the car, especially when considering fitting Mk1 rear light conversion panels as this will determine how much of the back panel needs repainting.
The other thing to consider is the condition of the boot floor, valance etc in that area, this could well kick up extra work in that area.
The brake conversion kit is straightforward to fit, as is the grille etc but body mods usually kick up one problem or another and could end up costing you more money.
If you really want it done the way you say, then you really need to pop down to a specialist and have a chat about your requirements and only then can you get a ballpark figure.
It is really hard to say on a forum when it comes to labour, because there are other elements that need to be considered which would require seeing and inspecting the car and above all else, price will vary between different places.
Have a look around on the traders area of the forum and see if there is anyone near you who can take on the work and at the same time, you will be able to see reviews from other people who have had work done there as there are some companies out there who do it only for the love of money and in no way for the love of the car and won't be afraid to overcharge or not do a proper job