there are loads of diferent things to try to gain you loads of extra distance BUT none will give you more benifit than having a lesson with either some one willing to teach you or better still a qualified casting instructor
Take a look in sea angler magazine,they have registerd casting insructors up and down the country,give em a call and they will give you the details of an instructor near you,as for cost...our local dorset insructor works for free .....so dont be put off by cost
I bought a video called Mastercast and watched it over and over again. It tells you how to tune your reel to avoid over-runs. Then you get to see Neil Mackellow, ground and pendulum casting in slow motion.
I can honestly say it added yards to my cast, I'm not up to full blooded pendulum yet but have found groundcasting really increased my distance.
You sometimes get these videos on Ebay, Look out for "Sea Angler Mastercast"
i agree with the guys see a casting instructor or get a video failling that there is alot you can do yourself like going down in sizes of your mono e.g 20lb down to 15lb use smaller baits or stream line it with elastic . fine tune your 7ht .have you got a rod that suits you is it to soft or hard ,to soft and you wont get the power to hard and you wont get the compression to throw your bait out.
the best way to improve your casting is to get the help of a casting instructor or a very competent caster. failing that the best thing you can do is go along to one of the casting comps. sometimes it can be a bit of a treck but it would be well worth the effort.
the current venues closest to your area are sutton vallence in kent. they are just outside of maidstone.
there is the weymouth casting club which have meets in dorchester.
there is also the surfcasting federation of wales and they cast inbetween bridgend and cowbridge which is a few miles the other side of cardiff, there next meet is this coming sunday. newcomers are allways welcome at club events.
i live just the other side of swindon from you, and i happen to be a casting instructor if you dont mind travelling down this way then i would be more than happy to give you some pointers. i dont make a personal charge, all i ask is that people make a small cash donation to the charity to which we belong. which is devizes contact a family.
Go see an instructor its by far the best way. Like TJ, Im a casting instructor also but i live in Essex so a little far away. Dont worry too much about tackle until you have seen an instructor who can put you right. Lots of people come to see me and think that their are short cuts to distance like reel mods ect, well Im afraid all the mods in the world wont help, its all down to your technique. Theres no short cuts Im afraid
I personally went from a maximum 70yd cast with baited trace to around 150yd simply by watching a small section of Casting from the Shore featuring Alan Yates. It changed me from an overhead thump style to a 'semi-decent' pendulum swing. What seemed hard to begin with eventually turned out amazingly simple.
Its pretty hard finding a casting instructor where I'm at and at about £5 from E-bay it was a bargain.