Okay, firstly I'd sort the main tank - play sand substrate (2.50 per 10kg from argos, or tesco do something similar for £1.00 for 10kg.)
Type java fern into ebay or just google it, look up the pic's then pop into your LFS to see if they have it - its pretty distinctive.
Main piece of bogwood centre, a clump of Java Fern either end (2 plants), break a terracotta pot in half and pop them either end leaving an open swimming area at the front of the tank. And then tinker to get it looking the way you want it - moving plants is alot easier with sand substrate than gravel.
Similar idea for the smaller tank, using the fake plants in a similar way. Thats how I'd do it, but that would be to my taste - most people will have a different one.
Edit:
And I second what minx says, don't change the tanks if you're happy with them - its what you like thats important. Theres some ideas above if you're not happy with them but its your tank ultimately.