I use Jennychem stuff, Hyperwax, it lasts about 4 months.
Its a part ceramic (Silica) coating. 1ltr does a long time at 1;50 dilution.
You slide off the car if you lean on it. Does the windows as well, better than RainX.
Apply it, snow foam or spray to a wet car, leave it for 5 mins and towel it off. Best results when you towel it off, give it a slight buff with a dry microfibre.
I ve tried a few treatments and this is by far the best.
No need to consult Motability either.