Hello Eileen,
I am so sorry to hear of your compost woes.
Sinclair who make New Horizon really should do better than this. It grieves me no end when gardeners lose time and even crops, as well as money, with useless composts.
Grrrr.
Right let’s move forward – I like the trials by Gardening Which, who are independent of advertisers. They always refer to what happened the year before so cannot be completely up to date with reformulations and yes, New Horizon is reformulated every year it seems. The contents you describe are just not good enough. Not to mention the lack of growth. I am emailing them at info@william-sinclair.co.uk and it will help if others who have problems let them know, and ask for refund or replacement at least; they need to know.
In the GW trials, their “Don’t Buy” recommendations include Carbon Gold and John Innes no.2. Their Best Buys all include some peat, mixed with bark or coir, and include Verve (B&Q own brand) and J. Arthur Bowers Traditional All Purpose compost.
For peat free they recommend Melcourt’s Sylvagrow, based on wood fibre and bark and it costs around £7 for 50 litres. The National Trust use this and are pleased with it. I use West Riding module compost which is based on peat sieved from Yorkshire reservoirs, but it is expensive retail.
As for sweetcorn, there is still time in the south of England at least, just and if summer is warm, sow tomorrow!