>>>Will I get a criminal record?
Yes
>>>should i turn up to court
You'd be mad not to because:
(a) the magistrates could issue a warrant for your arrest, meaning that you'd be taken there in handcuffs, probably have to spend hours sitting in the cells and then have your case heard by magistrates who weren't best pleased with you ; or
(b) the case could be heard in your absence, with the magistrates imposing a very large fine because you weren't there to fill in the form declaring your very limited means. (Make sure that you get that form as soon as you arrive at the court building - it's important!)
>>>Can I sue the guy for trespassing on private property
No. As long as they don't intend to steal, don't force entry and don't intend to squat in your home, anyone has the right to enter your land (including your house). You can only sue them if they refuse to leave and/or cause damage. You could sue for parking charges but only if you'd clearly displayed a notice, relating to such charges, before the incident took place.
>>>for defamtion of character by calling me 'racist'
You need tens of thousands of pounds to launch such an action, which you'd risk losing if the court threw the case out.
>>>and assault?
Since the police & CPS seem disinterested in pursuing a criminal case for common assault it's unlikely that a private (criminal) prosecution would succeed. To attempt it would cost you thousands of pounds. The level of physical/psychological injury suffered by you is too low to enable you to claim under the Criminal Injuries Compensation scheme and any civil claim by you would be expensive and time-consuming, perhaps (at best) resulting in £50 compensation (but risking you losing thousands of pounds).