Viscount grand prix

If you've been Googling, you've probably seen the Sport ones at bicycle decals and Bicycle stickers.
These are an adequate basic set, with the latter discounted currently to £10.00, making them good value to mark up your restoration as a Viscount. Bicycle stickers offer to customise colours at no extra cost, but I don't know if they can use the model name font to create a Grand Prix version for you. It might be worth a phone call to ask.

H.H.Lloyd are currently listing 'Aerospace GP' decals on their stock list, along with Viscount down tube and silver metallic head-shield and Aerospace specification stickers, enabling you to make up your own 'set'. Note: they are listed under A on page 1 of the A-K list, not under V. I've not used HHLoyds myself, but others speak very highly of them.

I had extremely good service from Velocals in the US, who made up a set of A/S Victor decals to my specification, including gold metallic backgrounds to the head badges and gold/white demarcation bands for the seat tube. The decals are lovely, and I managed to avoid the US to UK postage cost by having them sent to a friend who was on holiday there.

HHLoyds might be your best bet in the UK if you can get all the items you want from their in-stock selection.