Lidl do a mini oven for £20.
We are 13 months in of not having a kitchen. Have mini oven, microwave and slow cooker in dining room.
Buy lots of easy cook stuff - spatch cooked chicken in a big tray that you can add potatoes round and bake, ready made lasagne etc
Not having a sink is the hardest. I refuse to wash pots in the bathroom (yuk) but will tip liquids away and rinse odd thing there. We eat anything dry (sandwiches, toast) from tinfoil and reuse. Have melamine plates and mugs and take to a family member a few doors away each day to wash. (Real crockery is v heavy to carry, paper plates crap for hot food). Use sturdy plastic cutlery and reuse.
Once a week or so I go to my mums and prep veg and make dump bags up for slow cooker which can use straight from
Frozen . If I can I will batch cook curries etc at mums too for freezer. Slow cooker liners are your friend as no washing pot after.
Beans etc can buy in snap pots that go straight in micro. Micro rice etc. Porridge pots and frozen smoothie mix - kids take nutriblend cup straight to bathroom, rinse and put it back for next day 
It’s manageable but hard work. We have our old fridge which helps and use a lot of baby wipes. It is not eco friendly.