How seal large Gap tile to shower tray

[Angling mad]

shower tray cropped.JPG (217.68 KiB) Viewed 2329 times

I have had to dig out and reseal around a shower tray. Having got stuck into I have found that the tilers did not tile down very tight to the tray and the tray itself is not tight square to the wall probably because the wall is out. So I have a gap of the full tile depth plus approx 15mm by about 10mm along most of the back side of the tray which was filled with silicone. See Photo. It is a bit of pig to get it all out. Do I need to as it is so large and I will resilicone over it. I dont want to be doing it again for several years so What in your opinion is the best way to provide a robust long term seal. Thanks.

[toolbox]

Try quadrant tiles.
This sort of thing,

http://www.wallsandfloors.co.uk/range/w ... rant-sets/