There are no immediate consequences for the USC in buying a home in the UK. If you are in a position, in the UK, similar to a position in the US where you would purchase a property, then there are no reasons not to buy in the UK from a practical point of view.
Having said that, there are any number of issues that will arise which need consideration.
Are you sure you will be staying in the UK for the foreseeable future? Selling the home in a state of needing to offload it quickly in order to move back to the US (or another country) can create an uncomfortable situation. No surprises there. Owning a home can be a burden anywhere given difficult situations, like the loss of employment. No difference if in the US or the UK; but selling a UK home from the US or elsewhere is a challenge (but not insurmountable).
There are two types of ownership in the UK - Joint Tenants or Tenants in Common. There
may be US tax consequences and US inheritance consequences depending on the type of ownership. You need to investigate those consequences.
https://www.gov.uk/joint-property-ownershipSince all USCs are treated as if they are resident in the US, the US treatment of gains, deductible expenses, and periods required for living in the home (occupation) apply for US tax purposes.
http://www.irs.gov/pub/irs-pdf/p523.pdfYou also need to be aware of the consequences of having a foreign mortgage. There are rules pertaining to foreign financial
gains made on repaying the mortgage. You will need to be aware of this. A competent, UK/US conservative tax advisor will want to calculate this. You have a 50/50 chance of making a gain depending on exchange rates.
Currently, the IRS
may not be overly concerned about this (IMHO - and I may be wrong), but it is the law according to the tax code. Proceed with caution (and awareness of the situation). If the current war waged on US expats by Congress/IRS continues, it could become a very important issue (or IS an important issue, depending on your point of view).
As for the UK, there are two tax consequences. You are responsible for local Council Tax, and you will be responsible for Stamp Duty, depending on the price of the property.
https://www.gov.uk/stamp-duty-land-tax-ratesAn additional UK tax possibility will again relate to your occupation (or length of) of the property. There are, at present, no capital gains due on a property you sell if you meet the occupation period requirements, IE it's your main home.
http://www.hmrc.gov.uk/cgt/property/basics.htmThe last difficulty you need to be aware of (which is very different to the US) when purchasing a property in England is the right of the seller to back out of the deal at the last minute, with no adverse consequences. You will learn the meaning of "chains". You make an offer on a property; you sign an intention to buy it; the realtor
may ask for a minimal deposit; you have a full survey done on the property; you enrol the services of a solicitor; if you own a property, you may have agreed to sell it to a potential buyer; you pack all your belongings; and a week before
completion (the exchange of contracts between your and the sellers solicitors) the seller decides they don't want to sell the property. Tough luck. You then have the pleasure of informing the purchaser of your property that you have decided not to sell. Their tough luck. The "chain" collapses.
In Scotland, the situation is much more similar to the US (you make an offer, you sign an intent, pay some money, and basically you've bought the home and the seller has sold the home).
I'm sure it's possible I may have some of these points wrong, and it's quite possible others will be along to correct or disagree with me (especially concerning the gain on the mortgage), or make additions.