Grouting patio slabs ?

[gezt]

Hi , please can anyone advise on a grout (ie floor tile flexible adhesive/grout )that a I can use on my riven patio slabs that will stay put after frosts and pressure washing that have twice removed the mortar up till now !!
I am tempted to use a Wickes adhesive/grout, unless someone can advise a better product :?:
Regards Gez.