I'm planning a trip to the UK for the end of August/beginning of September. We're spending a couple of days in London before heading toward Brighton then to Salisbury and Bath. Then heading north to York and Edinburgh. We were planning on taking the train/transit to get around I was just wondering if we needed to pre buy train tickets or would be able to get them once we get there? And if we do need to pre buy tickets does anyone have a recommendation for a site?