No, 55W seems right. 40/45W is too low, that was with tungsten filament bulbs with the round base (can't remember what they were called).
Relay will be 20A not 20W. A 20A relay is good for 250W and should only drive the high-beam so should be fine. If the contact is getting hot and burnt, you are drawing too much current. Check to make sure the low beam filaments go off when you put on high beam. If the low beam stays on with high beam, you'll have over 300W so drawing about 27amps. If yo change the relay to 30Amps you are likely to burn the wires or the contacts in the connections.
Thanks Theo,
Yes 20A.
I have currently fitted outer twin filament Dip/Full 45/55W beam (with that round base, H4 im sure) and inner single contact 55W so on full beam I have 4 x 55W.
I hear what you say about the Dip staying on when the full beam is on, ill have a check later.
As my car is a 1600 Haynes manual definitely shows 40/45W outer with 45W inners.
The relay cuts in and out only on full beam, hope that is correct.
Steve