My current one is probably going to be dead in the next month or so because the roots are too damaged so I got two replancement ones from work for a quid. So my question in how to plant these two so they survive? My crurrrent one is in a pot with loads of sand and grit to improve drainage.
Rosemary is pretty tolerant. Plenty of sun first and foremost, good air circulation. The soil for your current one sounds about right - light, very well drained. They hate wet feet. What happened to the roots of the current one?
They do need lots of good drainage so it sounds as if you have that right. They need as much light and warmth as they can get, the harder you grow them the better the oils in the leaves and thus the better perfume and taste you get.
When we visit our friend in the very south Spain we walk among hot dry dunes and so forth, where the rosemary just is stunningly good - no soil to speak of, no rain for most of the year - the perfume is glorious. Guess that is what they like then.
Mine, which is Fota Blue, a lax variety, has been in a terracotta tub in a very sunny spot for more years than I can remember. I've never changed the soil in there - which was probably JI plus some grit. If the weather's very dry I might remember to water it. These conditions seem to suit it very well.
Mine is not very happy at all and with all the rain we are getting isn't helping I suspect.
The backstory for my question can be read here:
Just read the backstory. Any sign of fungal problems with the roots? They can get root rot. They can also, for whatever reason, simply turn up their toes. A couple of years ago I had one in the ground that simply carked it for no known reason. Went from thriving to D.E.A.D. within a month.