Posted: Today at 12:26
Hi Meomye, that is a lot of questions, so apologies if I miss anything!
Tomatoes: They will be fine in the 3" pots for now but when they are about 8-10 inches tall, plant them in their large pots, which should be about 10-12 inches diameter. Plant them deeper than they are in the little pots - bury the stem up to the first pair of leaves. Both of those varieties are 'indeterminate' aka 'cordons' and, contrary to the advice you were given, you do need to remove sideshoots which appear at the junction between the main stem and leaves. See here:
Do not start feeding until you see tiny baby tomatoes forming on the first flowering truss, then feed with tomorite or similar, diluted as directed on the pack but no more than once a fortnight, and don't water them until the top 1 inch of compost is completely dry or they show signs of wilting. Over-watering and over-feeding are the two biggest mistakes that those new to growing tomatoes make - controlled neglect will reward you with tastier fruit and healthier plants! Only ever water the compost, never get water on the leaves. You can grow them in the unheated greenhouse but I'd wait for a few weeks before putting them in there just in case it gets too cold at night - if you have a maximum-minimum thermometer, keep an eye on it and you are good to go when it doesn't get lower than about 6-7 degrees for a week.
Your peppers will probably be best in the conservatory as they are heat lovers and 8-10 inch pots are fine for them. No pinching out of sideshoots and feed with half-strength tomato feed once a fortnight once you see the first flowers. If the greenhouse is sunnier than the conservatory, move them into there once night-time temperatures aren't dropping below 10C.