Using UK switches in Slovakia
Electrically they should be safe and function well. Both are EU member states - so standards are theoretically harmonised. 

The problems may be that UK light switches are designed for use in UK back-boxes and patresses. The dimensions of the box and the location and dimensions/threads of the fixing screws (which are always included with UK switches) may be different to those used in Slovakia.  

Labelling of connections in UK switches may be unfamiliar to Slovakian electricians (e.g. "Com", "L1" and "L2") but that should be a minor issue.