That's what I use, in 9 or 10 inch pots, with the usual tomato food from when the first truss has set and they do just fine. Multi purpose compost is more or less what's in growbags anyway.

yes I use multi purpose compost too. Similar sized pots too. Once the first fruit has set we start feeding ours with tomorite or similar tomato food. Wilko's own brand has always been good for us.

I've done it too this year with tomatoes, cue and chilli plants. I was lucky my son had a huge multi purpose left which he brought here for me and I had a few bought before shielding and lockdown began. Got lots of tomato food ready to go also bought at the end of last year when gardening was finished in Wilko, so a great price too along with basket feed, so I'm set up hopefully.

I would grow in pots over growbags every time. More space for the root system and easier to control watering and feed.

I don’t use the grow bags to plant in, just the compost. Bought multi purpose compost and all tomatoes now potted up.