I started freelancing for a UK client, myself being based in the Czech Republic, about a year ago. I stopped working for them in April, after not having been paid for five months. This is specialized software consulting and the sum is substantial. My contract says I will not be paid 'if no services are provided'. They have agreed to pay for December, but for January-April they claim no services were provided, but refuse to go into detail. I can prove through communications that I provided services as requested during that time, received positive feedback, and was promised full compensation.
The CEO, who I reported to, is a pathological liar, and made up lies about family tragedy to distract me when I used to ask for payment. Now he is asking that I provide an account of each of the 22 days of each month for him to consider payment. I cannot do this honestly, because this is months ago, I have been locked out of systems, and when I was paid before, no such reporting was required. I hired a solicitor locally to help me, but he hasn't made any progress (or to be precise, there has been progress in the clients demands getting more and more impossible to meet), and sees the clients' "show me what you did every day and I might consider payment" as the options we have (he has not replied to me regarding what his strategy is, or what he is willing to do without it incurring extra cost, but it seems to be referring to my contract, but not referencing law or the supporting materials I have).
The client cannot show any evidence that I provided unsatisfactory services or none at all (and he has not even specified which it is) from the time before I stopped working there, only stuff that he is now making up to avoid payment. I feel like I might have hired this solicitor out of desperation and without researching things enough by myself, and without many options where I am located. What does this look like to more experienced freelancers, and what would be the resources and options I should be looking into at this stage?