Hi Ricky and welcome, I think it's probably important for you to research what type of spring and weight of oil you need yourself by contacting the companies AyJay has listed and asking for their advice based on your own requirements as this is a personal thing. It sounds as if K-Tech have recommended you progressive springs based on your requirements of something suitable for "just pottering around" as Progressive springs will generally give a 'plusher' ride under these circumstances and are what were fitted as stock by Yamaha (just not a strong enough spring) . Like AyJay I have chosen linear springs because I feel they are better suited to my needs which are more towards sportier riding and predictable action through the entire stroke. K-Tech also recommended me 10w oil which I think is a little too heavy, I will certainly be trying a slightly lighter oil when I come to change it, most likely the 7.5w AyJay has recommended.
Though a fork service and new springs will help, if you are still running the OEM rear shock the biggest improvement you will get in handling will be from getting that sorted, The R6 mod is a popular cost effective way of doing this if you can't justify a replacement shock from the likes of Nitron. Raising the rear with a jack-up kit and lowering the front by dropping the yoke down the forks will also give noticeable improvements to the way the bike corners.
Though a fork service and new springs will help, if you are still running the OEM rear shock the biggest improvement you will get in handling will be from getting that sorted, The R6 mod is a popular cost effective way of doing this if you can't justify a replacement shock from the likes of Nitron. Raising the rear with a jack-up kit and lowering the front by dropping the yoke down the forks will also give noticeable improvements to the way the bike corners.