There has been much discussion on this forum regarding Alibaba and a lot of it is not flattering. Most of the suppliers listed identify themselves as manufacturers, even if they are not.
I never recommend that site to my book buyers, instead I refer them to a few sites I know to be safe. In fact I see many different sourcing sites mentioned on the forum, but I have never seen anyone refer to the sites that I recommend as safe.
1,000 items (Chinese suppliers always refer to pcs., not items) would be considered a small order, but you should be able to get a manufacturer to attach your own brand labels. You may have to agree to pay for 5,000 or 10,000 woven or printed labels, and you would have to bear the jacquard cost, which could be a few hundred dollars.
The manufacturer would hold the remainder to use on subsequent orders.
You should ask for a quote FOB. Make sure they spell out FOB where??? I have warned in other posts that although international shipping conventions cover shipping terms, called Incoterms, many Chinese suppliers apply some of those terms loosely. Make sure that if they quote FOB it does not mean to them Ex Factory. The Incoterm for Ex Factory is EXW. There is a sticky on the subject but that is no help to you if the suppliers carelessly, ignorantly, or deliberately interpret the terms differently to the correct meaning.
If they quote EXW, or FOB factory, you will incur inland transport and other costs which could make the freight very costly.
Without knowing the type of clothing I am only guessing, but if they are bulky you might find freight cost a problem. There are UK based freight forwarders who advertise on this forum, and I would suggest you ask them to quote freight and other costs for you.
For them to do that, you will need:
1. Total weight of packages and the quantity.
2. All dimensions of packages .
3. Nature of the goods.
4. FOB point. That is the port at which they will be loaded.
If the clothing is made of leather, it may be economical to ship them by air. Just in case you are considering leather, take note that many Chinese clothing manufacturers will identify their products as leather, but they are in fact Polyurethane, or sometimes PVC. Some will state PU Leather, but others simply state Leather.
Before you finalise the order, make sure you negotiate payment terms. The most common terms for an initial order would be 30% deposit, remainder on shipment.
Quality control can be an issue. You must obtain samples before placing a full size order. If you want a range of styles, you will need to order samples of each. Ask the supplier to send these by air courier, but you must have a door to door quote before you finalise the sample order.
If the value is less than £135, duty will not usually be collected. If door to door, the courier will handle the clearance for you.
This post is not exhaustive, but I do not know how much you know about sourcing and importing.