After much experimentation I have settled on a set up for 500kHz that is giving me some good success.
The Antenna is an Inverted L, 6m Vertical and 8m Horizontal. The more Top Loading wire the better, however I don't have the space for several top wires. I added a lumped capacitance in the form of a disk 270mm dia and wire spokes.
The Loading coil is quite a large diameter wound with Silver Plated PTFE Insulated wire.
The PNP NPN pair PA produces some 500 or 600mW of RF at 50 Ohms. This gives an ERP of 200 to 275uW.
Results mainly using WSPR has brought reports from 32 different stations in 7 Countries.