Depends on the individual situation. The idea is that the (non earning/working) partner should ,as far as possible, be in the same finacial situation as they were during the marriage.
You want your solicitor to be like an attack dog Rugeley- stuff him assuming the opposition should be getting the lion's share. As Pete says get a more aggressive solicitor.
What is his reasoning? I'd be interested to know. Have you just turned up to claim your share after your wife has paid the mortgage and raised the kids while in full time education? The court may want to see yours/hers bank statements. start at 50/50 and go from there.