I bought some last year from The Welly Shop near Ross on Wye,They do mail order. I must say that they are the warmest , most comfortable boots I have ever had . I have vowed to never buy a pair of " normal" i e non neoprene lined wellies again.
Look on the www.belstane.com website - i am not sure if they sell them directly but they are the main distributors for them and will probably have stockists - I have a pair and I cannot recommend them enough - they are FAB! Hope that helps.