depends what you want. imo you can do a 2.1 zvh cheeply and get a respectable 200 bhp.

first off good 2.0 zetec bottom end. so you dont need any work done on the crank or big ends. £50-100

use let pistons brought mine £40 these can handle 330 bhp.

standard zetec rods good for 250bhp these will need machining to accept the pistons. cost about £30. also little end bearings ask your engine builder.

block will need machining about £80.

head bolts and conversion plates £30

cvh 1.3 cam belt tentioner about £25. if you cant find 1 contact me.

head gasket to allow the bigger bores, felpro £40 may get cheeper if you look around.

to be on the safe side arp rod bolts £60 and piston rings £50

think thats most stuff
total about £450

not the best build for over 250bhp but good for the money