Modern Vespa

Anyone any ideas on the import/vat on a new engine from India cost with shipping is £530 but not sure if worth doing if final cost going to be silly money.

Think it's normal VAT @ 20% but could be wrong, it's been a while.

Also some countries it's not charged.

Also some senders will mark the value lower to reduce the tax.

Thankyou for that. I know these vendors won't reduce the price on label unfortunately

Unfortunately, duty is only part of the equation.
Are they shipping it DAP or are you going to have to get a broker to clear it through customs? DAP means they clear it and ship it to your door, but you have to pay Customs fees and Duty.
Are there Government emissions or safety certifications necessary to bring whole engines in? Find out before it's sitting in an airport in the UK.
Find out what HTS code they plan on using. That will give you an idea of the duty you are going to pay. Find out if there's a better one to use, and if there is, make sure the shipper uses that one on the commercial invoice.
A good rule of thumb is that if the price of one once it's in the country is significantly higher, it's a PITA to import.
Something else to keep in mind is that if there is a problem clearing customs, which can be because the shipper didn't send all the necessary paperwork, or the customs broker miscategorizes it, you are going to start paying storage. Here's an example of how things can go sideways in the clearance process: I just had a delay in US Customs because the Fedex employee doing the clearance saw the words Wild Lion on an invoice and decided the shipper needed to fill out Fish and Wildlife paperwork, then, so as not to appear like she didn't know what she was doing after it was explained to her that no lions were harmed in making these parts, decided the reason she needed this paperwork was the word Sponge and she needed to know if the air filters had been harvested off the ocean floor. It took a week to straighten out. If Customs needs more information from the shipper, and they just left for a week, guess what doesn't happen.
If it's a one off shipment, you would be best served by finding someone in India who knows how to fill out paperwork so the package gets through UK customs as cheaply and quickly as possible.
If they can ship with one of the big three, Fedex, UPS, or DHL, it's worth more to have them use DHL. They are great at getting things through quickly. UPS is okay, and Fedex can get your grandmother to scream obscenities into the phone.
If it's being shipped in a container on a boat, unless they'll let you row out and pick it up before the boat docks, getting it home is going to be expensive.

Motovista addressed some of the issues that immediately leapt to my mind. I believe that at lest for now the UK is obligated to have vehicles that meet Euro 4 standard which India doesn't require so you may have compliance issues in addition to import duties. Definitely something that needs to be researched before you try to imp9ort directly from India,

Duty is about 3.5% but you have to pay VAT on the total.

so 20% of duty+ cost+shipping.

Which new bits do you need? Maybe just import those?

New engine number won't match log book etc..

Euro 3 should be okay still as it meets the ULEZ standard even.

Can you source one within the EU to save on duty, are the ones advertised by SIP in Europe or sent direct from India.

When it doubt, see what they cost on Ebay.
There are a lot of sellers shipping them to the UK, so it's got to be pretty easy, they actually get there, etc... If you ask any of the sellers, they can tell you what the duty is, because they've been asked before.
OTOH, there are sellers in the UK that are able to sell them for about the same price as you would pay to import one, because when you buy a container of the things, you are able to get a better price per unit.