Honeythorn
Sugar coating and nicely nicely? I don't think so
Yes, but not every person has the money to buy tanks...
I know you like your car boot sales but remember there isn't a car boot sale everywhere.
I know that, which leaves Ebay, Newspaper classified ads/free ads, Craigslist and garage sales( if in the US ) and even some fish stores sometimes sell ex display tanks. Plenty of places to get a bigger tank.
Even a clear plastic storage tub/rubbermaid tub 12 inches X 10 X 12 per fish Or for a divided pair - 18x 15 x 12 inches or bigger ( or the approximate sizes , TAKE A TAPE MEASURE ) will do just fine as a temporary tank until a second hand glass one can be found.
Plastic storage tubs are dirt cheap so getting one for each fish in the approximate size mentioned or for the pair is well within anyone's budget, even on the dole/welfare.
Betta989 - All the options I mentioned above are available to you for finding a larger home for your fish. Explain to your parents that you need a bigger tank for your fish to be healthy.
As I say, even a big clear storage tub will do, you can set it up with a heater and filter like a normal tank, you can add gravel and SILK plants ( never plastic ) . Just make sure to cut some holes at the edge of the lid for the wires of the heater and filter to come out ( so you can shut the lid properly ) and cut a few small holes in the top of the lid to allow air in. Very easy and cheap way to set up a tank