£1300?? are you taking the p#ss???
The boiler alone is over a grand,and yes that is trade price.
Add the flue,programmer, thermostats, Magnaclean,pipe and fittings,cleansing agent,corrosion inhibtor, oh and if it's all right with you lot some labour,you can see that £1300 or even £1800 is a joke.
I'd say to the OP that,that price is fair,especially for the Worcester which is the one I'd recommend.
Make sure a Powerflush is done before fitting the new boiler,which should be included in the price.
Shame I don't live near you.
Ricey and Ekona must have the same opinion as Stuarty,that tradesmen don't deserve to earn a living!