How can I find out if this is a Joboffer Scam?

Both are scams. No real business of any sort would use a redirect number (except, I suppose, companies that offer redirect numbers).

Both are scams

There are a lot of things that show this is a scam, but I will point out a couple of them.

-Numbers starting with 44-70 and 44-070 are redirect phone numbers that can be forwarded to phones all over the world. They are used by scammers pretending to be in UK when they are not. Legitimate business located in UK do NOT have 44-70 phone numbers, so any time you get an offer with one of these phone numbers, it is a scam.
-both have email addresses that tell us they are scams.

[email protected] is a free email address from mail.com. Real hotels would send out emails from their own domain, not free addresses.

Then look at the address for Shaftebury hotel: [email protected]
Look closely. The real website is http://www.shaftesburyhotels.com
Those two letters are the difference between real and fake. The criminals have registered a phony domain, shafteburyhotel.com, in order to make their scam more real. But if you were really talking to someone at the hotel, the email would be from something @shaftesburyhotels.com

Domain Name: SHAFTEBURYHOTEL.COM
Registrar: INTERNET.BS CORP.
Whois Server: whois.internet.bs
Referral URL: http://www.internet.bs
Name Server: NS1.ENTRYDNS.NET
Name Server: NS2.ENTRYDNS.NET
Name Server: NS3.ENTRYDNS.NET
Status: clientTransferProhibited
Updated Date: 08-sep-2012
Creation Date: 07-sep-2012
Expiration Date: 07-sep-2013