Have had a half wit plumber install a shower after a number of initial leaks am left with a leaky connector, this connector is fitted to a copper pipe which is wedged/butted up against a wall (am not sure with this pipe pushing the connector at an angle is causing the leak), or is it that the plumber has over tightened the connector. The connector has had its grip worn down by the plumber also.

Can't really be helpful here. Connector is not a very specific term. There are couplings, threaded adapters, unions and things like that. Don't really know what type of fitting the "connector" is.
Could you perhaps post a picture. Then we could better advise you.

I assume you have given up on the half wit.

If it is one of those "Shark Bite"- like connectors than yes, pipe should enter the connector straight without any side pressure. Back to you. Milo