I am for one really. really proud of you. Alot of people don't care that much about goldfish. I have a similar story of my 5 gf in a 10 gallon and I saved up for an 80, until they get huge and I sell them.

You rock my socks.

Still until you get a new tank get melafix.

60 gallon should be fine for a very longtime, Omce your fish get to big for that they should be sellable to a pond store. FOr about $50 each! Or 50 pounds (i know thats not the conversion rate for $-pounds, but the price is about the same for most things in the UK as in the US even though the UK money is twice as much.)

I really truely love your devotion to your animals. Thank you, they would say if they could.

Here are some more tips...

For your new tank get an aquaclear side filter.
DOn't get a "60 gallon" bubbler. The 10 gallon works the same, I use a 20 for my 80 and everything is fine.
Goldfish food isn't as good for goldfish as koi food is. Find some extreamly small pellated koi food that your goldfish can fit in their mouths.
Live plants eliminate some nitrates.

Anywho I just thought those tips would help.