I hope you used a laminate product that was recommended for occasional wet areas, such as your bathroom. If you didn't, your problems are only beginning, regardless of any sealing. If you did, the edges are probably hidden under your mop board (I think it's called skirting in the UK), and will be difficult to seal now. The most important thing to attempt is to seal near your tub/shower area. This can be done with a vinyl product made for such an area. It adheres to the tub/shower bottom edge and also the floor. It's trimmable and has an adhesive backing. It should be available at any DIY source. Don't, please, varnish or otherwise finish the flooring. The top layer of the laminate is sealed under pressure and any applied finish now will not penetrate and would probably not even dry properly. Having said all that, best of luck!