did you know:
our electricty supply is 230v 50hz ac America is 120v 60hz ac, their 220v kit will run on our 230v ac but it will run slower (wrong frequency) but the extra 10v (230 - 220 = 10) will do it no good, so as you said they will need converting
now the fun part
to convert it to 230v ac 50hz you have 2 choices
1) you can have the motors rewound to operate at 230v 50 hz (I used to work at a company that did that, as well as rewinding burnt out motors etc)
however you will also need to have any relays changed to (the relays will be what operates the start / stop function, although you could change all the starting gear too)
2) you could get new motors and throw the American ones away, but then you have to get motors that are the same physical size / atributes (other wise they wont physically fit) and you still have to change the starting gear
(You may also have to have a bigger supply cable to cope with electricty demand)
You willl also have to get it shipped from America (its doubtfull they will fly it over due to the size and weight, shipping is MUCH cheaper)
Then also you have not mentioned (you may have not considered) as you are getting them from America (outside the EU) you will now become an "importer"
To import, something into this country you will have to pay import duty AND V.A.T. to customs and excise
customs and excise will help you with this, but it is easier if you are V.A.T. registered, if you are not V.A.T. registered you will need to apply for a "special V.A.T number" (again customs and excise will help you with this)
while you are getting your "special V.A.T number" sorted out it is likely the company that are holding it (because you havent paid V.A.T) will charge you storage for it
in summary
you have seen something (on the net?) that is what you want but cheaper in America, you can bring it to the UK, pay the following.
Import duty
V.A.T
Storage
Transportation (from the docks it arrives at),
and after all that, when it is at its your house, you then have to have it converted to run on our electricty supply, and you have to pay for parts (new motor / rewind and electrician to fit it)
In case you are wondering i know all this because i have done it (more than once), except it was not electric and so did not need converting.
if you import something and do not pay the V.A.T. / decide it costs too much / not worth it, you can elect to have the items destroyed, if you do, ask to be witness to it, but you still have to pay for the goods in the first place and shipping
is it still cheaper? (i think not)
Let us all know what you decide, as i did say, customs and excise are very helpfull (but they would be, as they want your money, and they WILL get it,) big companies are V.A.T. registered and do all the above all time
no problem , i just wanted to let you (or anyone else who reads it) to know what you are actually letting your self in for.